What is the most arrogant thing you've heard someone say?

I was working with a group of kids, two of whom were very good at math, and one beat the other at some math related task they were doing. The other kid said “wow how did you do that?” He said “well I’m quicker and smarter than you”. He wasn’t joking. He was serious. Kid said stuff like that all the time and it made him difficult to like.