Paid actor

A player in a pvp game so terrible at the game or one that makes such a grave mistake, often to the advantage of an opponent, that you start suspecting if said opponent secretly paid them for that screwup. An example would be if a soccer goalie failed to save a very easy to save shot, some audience may suspect the goalie accepted bribes from their opponents to let in an extra goal or two.

However, its most common usage is not to actually accuse players of accepting payment to play worse as such cases are very rare in online games with randoms, but to make fun of people who played so poorly they look like they did.

Teammate A: Bro did you see how badly teammate B choked that easy win
Teammate C: (sarcastically) Must be a paid actor smh my head