What's the deal with Kayn?

Seriously, I can't wrap my head around this unit. Yone gets backline access, Kindred can do reasonable damage as the fight goes on and even Kha'Zix jumps around at least.

Everytime I try to play around Kayn though, he spins into some tank a few times before he inevitably dies. If the enemy frontline dies first, he kills their carries quickly, but at this point the fight is already won more often than not anyway. Help me make sense of the guy.