laing
A person who thinks they're the best and won't back down, even if they're clearly wrong. They also think they're the only one who can do things right.
You: I'm gonna win this game. Laing: No you're not. You: I'm the best. Laing: No, I'm the best.
Laing: I'm gonna eat the whole pizza. You: You can't. Laing: Watch me.
Laing: I don't need any help. You: You clearly do. Laing: I don't.