What is the most frustrating type of teammate you have ever encountered online?

For me, the absolute worst kind of teammate is the player who completely ignores the objective to chase pointless kills, and then spends the entire match yelling at everyone else through a distorted microphone.

They treat a team-based match like a solo deathmatch, refuse to communicate strategy, and immediately blame the rest of the team the second things go wrong. It turns what should be a fun, cooperative experience into an exhausting uphill battle.

What type of player tests your patience the most?