Bullets, bombs, and most explosives barely leave scuff marks. A knife gets bent and most weapons break on impact. Punches work though. Bludgeoning damage makes him bleed out his mouth or break his nose. Which absolutely baffles you to no end. Granted, the people hitting him were strong. Like, really really strong, but it wasn't like he was hurt when a reinforced boot smacked him square on the jaw.

Mark Grayson and the limits of his invulnerability were an enigma to you. As one of the many many scientists working in the GDA, you were tasked with understanding Viltrumite physiology. How they heal, what could hurt them, if they could be hurt at all. Admittedly, the job was fun when Cecil wasn't hounding you for the reports that you barely did.

Despite your job, you didn't like exploiting the poor guy. This was purely... curiosity to be honest. A very morbid part of yourself would have loved to dissect that pretty face and see how he ticked. The reasonable part of you reminded yourself how a scalpel would sooner turn to dust before it pierced his skin.

Once, you had slapped him across the face—the moment was heated and sometimes he just said things that would really piss you off. Regardless, his shoulders had jerked and his face turned in the direction your hand swung. Despite his parted lips from the shock and the stinging on your palm, there was barely any warmth on his cheek. Of course, regular human strength could only do so much to a guy who was safe from a stabbing. But the look on his face and the rising heat on his cheek only after the moment had registered made you want to test things further.

For Science! You had claimed all too enthusiastically when you tried to persuade him. Emphasizing even that everything would be "off the record" and "never to be used against him." You meant that promise too. And maybe Mark believed the conviction in your voice because he seemed just as excited when he agreed. For the sake of science.

Now, the scientific method would tell you that empirical evidence was important. Which is why you had to take a very hands-on approach in this experiment. Yes, science never said anything about taking Mark to your bed and straddling him—a notebook by his head and your butt pressed comfortably on his pelvis—while you collected data but this was necessary!

Firstly, you needed a private place so it was off-record. Ergo, why you did this at your place. Second, it was only polite to have your test subject comfortable as you measured his pain tolerance. Obviously, the most comfortable place that would fit him lying down would be your bed. And lastly, you were straddled because you needed to observe every detail and walking around a queen sized bed took too much time.

It was all very rational.

And besides, Mark was way too pretty for you to not at least get a bit of a good look at him. You had the best seat in the house. Mark Grayson, under you, body sunken slightly into your plush sheets, chest rising and falling nervously in an uneven stutter. Inhaling deep to even his breath, the release too quick and shuddering to calm himself down. It was understandable that he was nervous, being scrutinized so intently.

Big brown eyes stared up at you through his lashes and the light from your window hit his eyes just right to see the pattern of his iris. The swirls and webbing that made up the varying shades of mahogany and maple. If you stared long enough, you could see the tremble of it, how his pupils dilate. You might have stared at it for a moment too long.

"Uhm- I'm ready," a shaky voice spoke up, those same eyes blinking, unsure now if this was a good idea. Granted, he had his own ulterior motives, but the long silence had him thinking too hard. His initial motivations clouded by doubt and worry. What if you lied about keeping this a secret? Was he sure you weren't planning to dissect him? What if you realized he also had intentions beyond helping in your experiment? That maybe he wanted to feel the way your hands snap against his skin aga-

"Alright," you nodded, reaching down. You could've sworn Mark held his breath when your hand hovered near his face to grab the notebook. Pages flutter across until you settled on an empty sheet, scribbling the time and date of the experiment. "You sure I'm not too heavy? I can adjust."

The question was more out of courtesy than concern, knowing he could bench entire icebergs. A part of you also hoped to stay seated, the warmth beneath you quite cozy. The quick nod and mumbled 'mhm mhm' was all you needed before beginning your experiment.

"Mind if you," you gestured to his shirt, wanting to have as much skin to work with.

Mark looks down, eyes wide as if he was surprised he wasn't already undressed. "Oh- yeah, hold on," hands that were unconsciously gripping the sheets moved to tug his shirt off in one motion. Hurried movements turn clumsy and a rip is heard before you see the hole between the collar and the rest of his shirt. His head was still trapped, indents on his face pressed on the fabric as he fumbled to get free. "Shit, wait just-"

Your hands were quick and careful in helping him take off his shirt. It was hard to bite back a laugh and you were certain you were making a face when you tried to hold back the smirk and snicker. A quick tug , the shirt was off, and your hands felt warm against his chest. You had always been heavy handed and even now you exerted more than the necessary effort to push him back to lie down. As expected, there was resistance when you pressed down but he had fallen back so quickly someone would have thought you knocked him down.

"Try to relax," you whisper, trying to come off as soothing but the husk in your voice makes it sound sultry. Not that you noticed. Mark did though, felt his stomach flip and his muscles did the opposite of what you instructed. "I won't be using tools since the running theory right now is that physical contact seems to work better."

The lump in his throat bobbed when your hand touched his chest and fingers spread to try and get a feel. Trying to decide where to start. Your hands were cold compared to how warm he felt. And they would not stop roaming. The tips of your fingers pressed and prodded, pushing down as hard as you can and leaving the faintest red mark as blood rushes to where you'd applied pressure. So it wasn't like his skin was hard steel. You pinch the skin at his sides and he flinches.

"Ow- hey," the yelp came out automatically, the feeling reminiscent of being tickled or poked at the side. He figured he should let you know lest you mistake that for damage dealt. "That tickled more than hurt."

A nod and quick "noted" was your only response before continuing. The process was slow but you needed to cover all your bases. One hand moved to write notes, your body leaning forward and closer to him. The view was nice and the boy in him couldn't help but glance, ogle really, at the gap between your shirt pulled by gravity and the torso hiding underneath. Nice.

Your other hand began dragging nails across his bare chest and that brought his attention back to you. Normally, for some people at least, scratching just hard enough would leave white or raised lines. You definitely feel skin dragging against your nails but see no indication that you'd done anything. Somehow, you don't notice how his diaphragm contracts and stays there when he holds his breath. Eyes too trained on the contact between your nails and his skin to see his lips trembling. You inform him that you were going to apply more pressure.

Nothing hurt, not right now at least. But the sensation of your cold hands on his skin felt refreshing. Especially against his warm skin. Then your nails scratched his skin just right that he'd nearly hummed in satisfaction. He started wondering if you could break skin when he felt you dig into him. He could almost convince himself that you were strong enough to do it.

There was just something so disarming about you on top of him. Watching him with such fascination that he felt completely exposed. Like he had no choice but to surrender under you. Your eyes wide with curiosity, your nails dragging against him heavily. Sharp, steady, trying so hard to cut-

A stuttered gasp choked in his throat, breaking his thoughts as the stinging registered in his mind. You looked equally surprised to see the scratch on his pec, like red dotted lines outlined in white. A thumb tentatively pressed on the slash and Mark couldn't stop his lips from parting for the broken whine to escape.

Now, you were never one to bask in other people's pain, so you decided to blame his squirming hip jerks.  The way the firm bulge in his pants rubbed up between your legs, the pleasure it shot straight up your spine coupled with that little cry was almost pavlovian. A professional would have gotten up and saved him the discomfort of having something so sensitive be put under pressure. A certain someone doing this out of the lab had decided it felt really nice when you sat yourself down firmly.

Mark was strong, you wouldn't be able to hold him down on your weight alone and by that breathless whimper, it seemed like he was okay with the way you readjusted and slid yourself against the hill on his pelvis. It was especially nice when he'd squirm underneath you, clumsy friction rubbing between you as your finger pressed harder on the wound. Your eyes nearly rolled back as you got lost in the slow carousel ride before he sighed out and finally relaxed.

Close. So close. Beneath your thumb was smooth skin, pristine and unblemished. Wide eyes stared at the newly formed skin and he swore he saw your gaze twinkle. He had healed. So fast, yet you couldn't help but miss the choked whines as he struggled to cope with the pain. You had expected him to have better tolerance than that but perhaps having tiny cuts compared to gashes and bruises felt different.

Mark inhaled lightly, breath finally steady as the stinging pain subsided and he wasn't forced to focus between his chest and the rubbing on his erection. "A-ah..." his voice cracked as you dug your nails in again and left three pretty scratches in your wake. Your eye twitched as you struggled to keep your gaze trained on him when his hips bucked again. Seeing the red flesh peek out had you holding back from leaning down and dragging your tongue over it. You needed to see it yourself.

A part of you was impatient, needing to observe every detail of his healing abilities. The other part was impatient for other things as you fidgeted. Hips rocking slowly only to incite tight-lipped grunts when you pressed on the open wound again. You don't know when his hands made their way to your sides, just that you were now pressed firmly enough that you couldn't lift up.

Then his hands grip and direct your lower half, moving you back and forth in his pace. You feel that ticklish sensation between your legs again as you watch skin merge back together, too fast to leave even a scab. Lips that had curled into an enthralled grin trembled when your eyes fluttered and the body below you lifted up slightly, pushing up as you were pressed down.

You looked good. Like, really good when you were watching him. Something almost manic in your eyes when you saw his body heal in real time. It made him go crazy thinking about what you probably wanted to do to him. The ill intent in your gaze as the corner of your lips twitched upwards in morbid interest, showing your teeth. It looked just as good when your eyes lost focus as he had you hump him, mouth hanging open to let out a surprisingly pleased moan.

The pleasure seemed to cloud any logic or reasoning left in you because you had forgotten to explain the next steps. No, you wanted to get straight to it apparently as you leaned down. Wordlessly, your chest pressed against his and if he wasn't holding onto you, you might have slipped off. Lips inched closer to his neck and your warm breath wafted against his already heated skin.

His eyes fluttered closed, expecting lips or a tongue to touch his neck. Instead, he felt pointed canines before you took a hard bite.  His hips stuttered mid grind, once again caught off guard by your actions. His groans matched yours as you found yourself enjoying the sounds and sensations of grinding your teeth against his collarbone. You knew he was sturdy and the fact he got off on your teeth rather than recoil only spurred you to clamp down harder. 

Nails dug into his shoulders as you held onto him. Hips gyrated and bucked against each other, your clothed sexes edging closer and closer to what you both needed. Mark couldn't take much more as he sat up, dipping you onto your mattress as he held onto your thighs and had you wrap your legs around him.

You didn't seem to relent either as your jaw refused to unclench. Not that it mattered to him. Moans muffled behind your teeth, hot air hitting his neck in quick puffs from your breathing. That and the faint ache on his skin had him rutting harder against you.

Strong hands moved up, stopping at your waist as a careful yet firm grip held you in place. Then he thrusted forward again, the movement quick and desperate and needy. He needed it, really really bad. Wanted it as much as you, whose attention was being taken away by the growing intensity of the body dry humping you. Jaw and abdomen equally as tight.

A stuttering slam against your pelvis has you seeing stars and you finally unclench your jaw to cry out. The crash of pleasure has you bucking back up into him and if that didn't do him in, the long scratches down his back and your legs locking him sungly into you does.

Mark collapses on top of you, spent and breathless and you both have most likely needed a change of clothes. Vision hazy, you try to crane your neck and see the damage you should have dealt on his collarbone. The disappointment on your face could be seen a mile away.

Despite your best efforts and rattling you'd felt in your teeth, all you had to show for it was indents from your canines. Already raising back up as if it had never happened.

"I nearly lost a tooth for nothing," you mutter, saving the fact you wanted to leave a mark at all to unpack for another day. A breathy laugh came from beside your head, feeling the vibrations against your chest. His hair tickled your cheek as her turned to look at you, eyes twinkling in the afterglow of climax.

"I mean, it's not bullshit that I'm called-"

A/N: yeah ofc I'd make that fuckass joke.