A type of person who needs to be taught a lesson.
Lots of people have natural competitive streaks, and that's okay as long as you know how to control it. And if you're a mature adult you can probably do that.
So what what's wrong with those people who can't. You are 35 and you beam with pride when you are beating your nephew 35-16 in Boggle, instead of thinking that maybe you need to take it easy the next round. Not let him win, just take it easy. That would be the normal thing to do. Do you still think the normal thing is to play 100% of your game in all situations? You need to be taught a lesson.