Token Evil Teammate

He's a bastard, but he's our bastard— Richard Nixon (on then Nicaraguan dictator Anastasio Somoza)

If your characters are part of a group of protagonists, chances are good that one of them may be the group jerk to some degree. Sometimes they're a selfish pest whom everyone has to put up with, and sometimes they can veer into outright evil. Before writing them in as an easy path to inter-group conflict, it's vital to answer the following question: why is this person here? Fortunately, there are lots of credible answers that can give some structure to their story arc. Logical reasons for this character to stick around include:


They have a critical skill which outweighs their bad qualities. For example, if they're the only one who can fix and operate the spaceship everyone's stuck on, the other characters are basically forced to tolerate their antisocial shinanigans or be stranded. This also includes people who have access to money, social connections, or other resources the group desperately needs. They're a teammate's relative. This works especially well if you've established the characters' culture values family loyalty no matter what.  They have power or connections. Maybe this character is the office supervisor or the ship captain. Or maybe they have powerful relatives or friends who will come down on the main characters like a ton of rocks if the jerk comes to harm. They're bound to the group via magical contract. In a world with supernatural elements, perhaps this character got stuck in a contract with the group, and they're forced by magic to put up with each other. Proximity. In situations where characters can't really control their social group, they can easily get stuck in situations where the best solution is to make nice with people they don't like. They share a goal. If the end is important enough, the characters have a strong incentive to cooperate. The hero wants to keep an eye on them. Perhaps channeling this person's efforts for good is better than leaving them to their own devices. 

If you come up with a compelling reason for the Token Evil Teammate to stick around, you have an endless well of possible conflict and potential plot twists to work with.