Sore loser of course.
But 1v1 is not balanced, and some classes can actually exploit their abilities, *THAT* would be something to point out negatively.
One of the prime examples is a rogue vanishing and recuperating to full HP in stealth. If someone does that, I just mount up and fly up in the air. Which is just as stupid and annoying and game-breaking as healing up to full without any possible counter.
Plus, rogues and mages have a big enough toolset and enough control to be able to win almost any duel, so...
1v1 can't be taken seriously anyway.