A Weevilton
A Weevilton is a person who thinks they're the only one who ever wins and everyone else is a total loser.
You: I got 85% on the test. Weevilton: I got 100%. You're still a failure.
DM: 'You didn't do your math homework. Again. I'm not even mad.'
In class: Weevilton says the answer is 3. Teacher says 3. Weevilton says, 'I knew it.'