Someone who radiates the main character syndrome often thinks or sees themself as someone they imagine or want to be like, or is pretending to be the lead of their own story or self-created tale.

The most common reason why people always ban Yasuo is the perception that any Yasuo on your team will feed and troll the game, while when he's in your opponent's team, he will carry the game by himself.

Yasuo Syndrome
When someone decides to try and fight the enemy team, despite the fact that you are under-powered.