When someone plays a game purely for winning and not for enjoyment. Don't get the wrong idea though as tryhards develop enjoyment from winning, but toxic competitive feelings ensues whenever they lose. Eventually the main motive will shift to purely winning, and they will less enjoy the game. This is coming from a tryhard.
You aren't the same when you go full-on tryhard versus when you play the game for casual entertainment.
Someone who spams something annoying to piss you off in a game then kills you in the most annoying way. Whenever you kill them they make up a stupid reason for how they died.