We're playing online.
I don't like the player, not the PC, the PC themselves is fine, which kinda makes this worse, if it was the PC, I could chalk it up to good RP.
This player also isn't unlikable/overtly terrible like in rpghorrorstories where I can call them out that what they're doing is wrong or something. They just make annoying jokes a lot of the time, making fun of everything happening in game (though to be fair and respectful, their own character is also the butt of the joke sometimes) and are weirdly specieist to certain things in D&D (mostly to monstrous races believing all of them to be evil), not the PC is specieist, the player (and the DM has established that as objectively not true in this campaign world).
I think this is mostly a difference of opinion rather than outright them being a bad player (though I certainly think so, since I'm biased).
The campaign is reaching a point where I and my character could leave without causing a problem (i.e. not during combat and stuff), so I've been thinking of just leaving, though I've also thought of telling the DM that I won't leave if the other player is kicked out, but I don't want to pseudo-blackmail my DM. I also don't think talking would just solve this (we've already tried talking with them about the specieist point, and they haven't changed, and I think I'm really the only one that finds their jokes annoying).
I think the best thing that would happen is if they leave of their own volition, which I don't want to instigate by antagonizing the character in game and stuff because I don't want to be a terrible person/player, and ruin everyone's fun.
Best Answer
This is your problem
To be clear - you don't like the player because you find them unlikable. This is not a character flaw in either of you - we like who we like and dislike who we dislike for all sorts of reasons, most of them irrational and personal.
Since it is your problem, don't make it about other people - either the DM or the disliked player. You need to decide if playing in this game gives you more pleasure than grief - if it does, stay; if it doesn't, leave.
People come and go - this time it might need to be you who goes. There's plenty of online groups looking for players out there.