@Quince, but why you kick a player on the last floor (or 2nd last, doesn't matter)?
You're wasting a lot of time of such this player. And your answer is definitly not a argument to kick someone. Just if it doesnt match with your playstyle, doesn't mean you can kick everybody to waste their time.
I could kick every single dungeon at least one player, cause they are bad as hell. But as long as it works, i don't kick anybody. And if someone is really annoying, i'll kick him directly, and not at the end to waste as much time as possible. Cause that is definitly not fair.
And why you didn't communicate with him? Did you know that it is possible to write/chat with everybody in your group? Why kick before endboss, why not earlier?
Players like you should definitily deinstall this game, so you can't waste more of other players time.