Tanks, and their overwhelming power in every game I play.

IMO tanks have always been a little too strong, but in the past you could deal with them with a little outplaying. Every single game I play I notice more and more that tanks are providing little-no counterplay. The only items that sort of "counter" tanks are either only useful on some champs, or a futile attempt at doing damage. You can get black cleaver, LW, and blade and still get trounced 10 times out of 10 by an amumu with a thornmail. You can play just about any ap mid with all the Mpen items and your full combos/sustain won't be enough to kill, or even escape, a tank past mid game. Even when you do manage to kill a tank as say, vayne, it took you so long that the entire enemy team is now behind you and you get murdered, or even aced.

TL;DR tanks are becoming way too strong in this meta, and it's getting incredibly annoying having to deal with teams that are made up of 3 tanks an adc and a mid.