A person with below 0 iq, which is impossible in itself, but somehow the children below 9 who play him achieve it. Yasuo is the only kid friendly champion in league without any NSFW+ ties online because only children play him. He is the most cancerous champion in existence, second only to Teemo, the devil himself.
Derived from the game League Of legends a Yasuo main has accomplished nothing and will never do anything in his life, they are usually stuck in this bubble where they think are awesome because they play someone who takes no skill.
yasuo main: hi i'm a yasuo main normal person: you shall be purged with fire you waste of space
That one person your team in any competitive game who singlehandedly loses the entire game, regardless of how well you and the rest of your team is doing.
Player 1: Oh man, i got counterpicked again.
Player 2: Don't worry, that guy is also a Yasuo main.
A person with stage 5 cancer and brain damage that still tries to live and play League Of Legends. Usually they are known for feeding, inting, throwing, (Usually leaves/disconnects from the game) and blaming their jungler for not ganking them even their jungler is a lane away. The literal and definite meaning of a uselessnarcissist.