Story's in comments.

Harem troubles.

Why Gravity falls Victor would absolutely hate James.

Where the hell do we even begin?

If James and Victor ended up being friends then it would be more Victor hating James and James continually taking the absolute piss out of Victor and his insecurities and all his trama.

As we have seen Victor is petty and prideful to an almost childish degree, despite being a teenager or adult. He wouldn't be able to handle James and his shit talking and take pretty much everything James says seriously. The reason why he wouldn't be able to handle James's shit talking is because it would bruise his inflated ego and pride.

James however is a different case,because of his compulsive need to take the piss out of anyone and his trama,James doesn't have an ego or if he did he'd quickly shuts it down and he'd allow people to take the piss out of him and make fun of him unless they hit a little close to home like something that's recently happened to him which would more than likely hit a nerve of which James would sock that person.

Victor is too proud and egotistical about himself to let anyone make fun of him or joke about him and due to his trama he tends to think that he is entitled to do whatever he wants and he can get away with it without consequence and James is a similar but different case.

James does do whatever he wants but it isn't out of entitlement or ego. James has been hurt and treated like shit to the point where he just doesn't give a fuck about what the world thinks of him but despite being a bloodthirsty sadist,James isn't without morals.

The people James doesn't kill are children and people he considers innocent and he doesn't betray the people who are loyal to him. If your loyal to James then he'll be loyal to you.

If James saw Victor hit or even go to hit a child then Victor would get his ass beat until he dies or is beaten to near death. And if Victor did get beat,I imagine that Victor wouldn't take kindly to someone beating the fuck out of him because of his easily bruised pride and deflateable ego.

How Victor even has children in his own universe is beyond me. This guy is a complete asshole like his dad!

Don't get me wrong,James can be a dick when he wants to be and that's because of the banter that he can have with people who can understand him. If your wondering why James doesn't have any friends like Victor has,which he probably treats worse than his enemies,is because James wasn't accepted in society and had a life of isolation,fear and deep seated trauma which lead him to becoming anti social and the bloodthirsty yet loveable lunatic we all know.

And in terms of relatablilty,Both characters would be very relatable to each other given that James has been abused,physically and emotionally like Victor has but the difference was this.

James has a disability which is his autism,inherited by his mother and that seemed to worsen as his mistreatment through his life and not only that,James was constantly abused and raped at the age of eight. Victor didn't suffer from such a fate and while you can understand that people have rough upbringings but it still doesn't anyone the right to be an asshole to anyone.

The main reason why Victor would hate James would be because of jealousy. Victor would be jealous that James has a carefree and unhinged personality as well as James actually having compassion,although not really much but it's at least there.

Victor however is a bitter asshole who can't see past his ego and humble himself before someone and can't take responsibility for his own actions. Like many abused children,Victor would probably go on with life with being miserable and lonely much like James has,however the difference is this,James learned and bettered himself from his traumatic experiences,Victor let the bitterness and his emotions control him.

In Victor's mind,James would be a mere obstacle in his way and say if they both did suffer the consequences of their actions,it's gonna be James whose gonna be the more mature one and take responsibility for his actions and suffer the consequences of his actions.

As for Victor,he wouldn't take any responsibility for his actions,he would just shift the blame onto someone else than to admit to his faults and swallow his pride.

Victor would also be jealous that James has a loving father,despite being the Grim Reaper himself, and he doesn't. The only family that Victor would have is Julie and Sandra. Another reason why Victor would hate James is because of this very simple reason.

James would call Victor out on how much of a complete bastard Victor truly is and would tell him the truth. If Victor did hear the truth and James calling him out then that would fuel his hatred for him,If Victor is as petty as he is in the gravity falls story then he won't be able to have good hard look at himself and actually feel guilty for what he has done to his friends.

And would want James to shut up and would try to scare James into shutting him up,which wouldn't even faze James at all given that he wouldn't even flinch at Victor which would anger Victor to the point of a violent outburst.

If they did fight then I think we all know how that would go down. With Victor getting his head kicked in much to his already fragile ego and easily bruised ego.