Why the hell not?

Zero Membrane

From the blog @zero-nephilim and a younger version of @aik-membrane

Strength:

Metal arm capable of crushing skulls and punching people's heads off their bodies.

Pain, drug, and exhaustion resistant thanks to traumatic training.

Has fought and killed people twice his size.

Physically strong, even without the robotic arm.

Has an armored suit inside his collar that allows him to fly, shoot lazers and stun grenades, and resist stabbing and lazers.

Sort of can use magic to control trees and some plants.

Has a medical magic that he misuses as defensive force fields.

Has no problem killing.

Weakness:

His robotic arm glitches when he's upset and can injure him.

Can't talk. (Only a weakness because he won't be able to poke at Sal's emotional weaknesses.)

Any trees or plants he makes with magic are very flammable and will cause him pain if burned or damaged.

If forced too much, his medical force fields will pop and cause him internal bleeding and heart problems.

May give up half way through the fight thanks to depression.

Mention his brothers, he will become an emotional out of control target.

Sal Quinton

From the blog @just-some-kid-named-sal

Strength:

Physically strength.

Insane stamina.

Doesn't need to rest very often.

Can shoot lasers out of his extra limb.

His extra limb is made of alien tech and completely under his control, it is extremely strong.

With it, he can also possess and control other electronic gadgets (usually ships and robots) be grabbing onto them.

Practically impossible to wound, even if he does, he can be healed in minutes with no scar. (It is possible, but you have to know how to hit him.)

Weakness:

Will do anything to avoid killing anyone.

Self loathing and can be distracted by taunting (luckily for him, Zero can't take advantage of it.)

Can't defend himself very well when attached to an electronic.

Similarities

They both like dark colors and have a depression streak, though Sal keeps his hidden slightly better. They're both used to fighting aliens, they're surprisingly good with electronics, and they're completely capable of killing on accident.