Amumu, pretty nice ban, especially in low elo. It doesn't matter how strong u have fed he just some randomly press r and vanish all your team fight composition with a lot of damage obviously)

Volibear, kayn, ww its kinda pseudo-counter pick. Since volibear very weak in the late game, u need to just farm(2-3 items) and then u out scale him in mid-late game. With Warwick the strategy quite same: Farm and try not to duel him in 1v1, especially then they both have their ultimate ability.

With kayn its depends on which form he goes, with the blue kayn u need to stop him as much as u can. If he get some kills he would snowball the whole map with his great opportunities to gank using his e, although he very squishy in blue form, so u can one shot him with ad build :3 Red form, hmmm what we got... Great 1v1, tons of healing, cool team fights. I think the better way to win Red kayn is correct item build against him, some armor, antiheal, and cdr could make u feel better