RIOT give us an item to counter master yi!
 

When there is a master yi on the other team it is so hard to counter except if you have a stun or fear or something like that. But mostly there isnt any when i play. He's just heaps hard expect if you whole team focus him but by that time like 1 guy is dead and another guy is at half health then the other 2 guys on yi's team just cleans u up. Please give us something to counter yi.

Thornmail

they took thornmail out!

EXhaust

Frozen Heart.

Randuins

Cc

If you're ranged, just poke him. If you are melee, wait for him to attack you. Stay behind your minions to draw aggro for them.. You dont nees frozen heart, you just need a brain...

pretty sure no one here is talking about his laning phase.

I'm confused by all of the slow items being recomended...

I don't think Yi is OP or needs any counters, but it sounds like the OP means unless you have 2 stuns or a stun and pop up to use on Yi he can escape too easy.

@OP:
He is supposed to do that. That's kind of his thing.