jealous/possessive Clark headcanons?
To start off this whole list is heavily biased and has nothing to do with canon is any way shape or form. Canon is my bitch and I use and ignore it as I please because I'm having fun, not writing a weighted thesis on any of these characters lol.
Contrary to popular belief, Clark has always been a jealous person. He's someone who feels fundamentally alone most of the time, so whenever he finds things/people that can tether him to Earth, he becomes quite possessive of it.
As a journalist, Clark has been exposed to the darker side of the world, the world which is full of dog-eat-dog people and it taught Clark to always clutch the things that are precious to him closer to his chest to prevent himself from losing them.
Clark rarely ever gets possessive of inanimate objects. The few things that are nigh precious to him are his baby blanket from Krypton, the teddy that ma kent made him when he was struggling with his powers and the first watch that his pa gave him and the kryptonian rose that Bruce grew for him. Other than that there really is not much that he cherishes more than life. (I'm not well versed in canon inanimate objects that are precious to Clark so feel free to add more)
He loves his parents, his friends and the league but no one ever comes close to the flame that Bruce holds in his heart.
Bruce is the only human on Earth who Clark thinks of as his equal. It's not a matter of power or Clark seeing anyone beneath him, no. It's just that no human in the world has Bruce's intelligence, his will, his inherent goodness and mercy, and no other person fascinates and pulls him in like Bruce does.
Clark has always been somewhat protective of his status of Batman's first real friend in the league, he loves the fact that he was the first one to decipher Batman's grunts and batspeak, he loves the fact that he's the designated person that heroes go to understand what's going inside Batman's head or to help them convince Batman for something. The status of Batman's best friend is very precious to Clark.
When they finally fall into a relationship after years of will they or won't they, Clark is hellbent on never losing this again, he finally had Bruce, he has tasted him and he would never ever let it go. This obviously spirals into a raging case of codependency and anxious attachment.
Clark hates the amount of people in the league who are crushing on Batman, he has tried to be polite and subtle but when it doesn't work and Batman keeps getting proposals Clark throws away all his politeness and resorts to mark Bruce and cling to his back like a leech in front of everyone to make it clear that batman is taken.
Clark once legitimately tried to laser a goon's hand for slapping Batman's ass but he was stopped by Bruce and was scolded thoroughly.
Ma and pa Kent are aware of Clark's obsessive tendencies and they firmly tell Clark to never force Bruce into anything he doesn't want and they have a discussion with Bruce too about it.
As soon as they are together, Clark is already prepared to make their relationship public and Bruce acquiesces without much protest because he feels too old to play those games anymore and Clark is very precious to him and he wouldn't want to disrespect his partner like that ever.
After the public announcement Clark never leaves Bruce's side at all, he's present in every function with his arm wrapped tightly around Bruce's back, he won't let anyone walk over him and/or flirt with Bruce at all. His intelligence turns Bruce on so much that they have to leave early every time so Clark can fuck his brains out like he's been desperate for.
It doesn't take Clark longer than a year to officially propose to Bruce and get wed.
They have multiple weddings. A private one in Kent farm, a grand one for the press and an intimate kryptonian ritual to bond them as mates for the rest of their life. Clark couldn't be happier(he cried in every single ceremony and it made Bruce bawl his eyes too).
Bruce is covered in hickeys and hand prints all the time, the marks are heavily concerning to normal people and even their friends were skeptical at first, but Bruce adores them. He feels happy being the subject of Clark's possessiveness, it's quite an experience.
There have been multiple cases of alien dignitaries trying to hit on Batman or asking his hand in marriage in return to leave Earth alone and Superman delights in beating them up a touch harder than usual and making it clear in loud and clear words that Batman is married and that Superman can fight.
Despite being absurdly possessive and having toxic obsessive tendencies Clark has never once actually crossed Bruce's boundaries, the rare times he came close to doing that Bruce told him immediately and they talked about it before finding a common ground (actual communication I know lol(also I'm basing this on my happier superbat variants not on my darker superbat, that's a whole different world))
I'm sorry that it took so long for me to answer this bb, but I was trying to make it at least somewhat cohesive and structural but as you can see I did not do a great job of sticking to my resolution, but I hope that you enjoy at least some of it nonetheless.
As always spare my grammatical and spelling mistakes, I'm quite illiterate.