Learn English – ny word for someone who makes many enemies

This is a bit of a neologism, but I suppose "self-saboteur" captures the person you are describing adequately.

If you don't necessarily need a single word you could go with the more traditional:

He has a habit of shooting himself in the foot

Some possible ideas for you:

A go-to player:

She's the team's go-to player [=she is the player that the team relies on] when they need to score late in the game.

You can also simply state that X is a most important player (MIP) or most valuable player (MVP) for the team.

The teams that rely heavily on one man to win a match are called one-man teams:

With Neymar gone, suddenly Brazil’s ‘one-man team’ lacks a man. (source)