tis yi is jus Q at u and ur dead in 2-3 hits even more scarier then teemo how do i counter yi other then using jax i tried many champs and ideas and yi jus penta our whole team several team hes so hard im so mad how do i stop such monster
From my games if the Yi isn't too high skilled, Morgana is very effective against Yi as trading damage is much easier
, 
, keeping out of melee range, hard CC for the ult, hard CC for any occasion.
He is a glass cannon with no range aside from his Alpha Strike. CC and beat him to death or back away. If he's blindsiding you, 
Attack speed reduces the cooldown of his Q. If you reduce his attack speed, you not only decrease his auto-attack damage output, you decrease his Q damage potential. A well-placed cc in the middle of a teamfight is also a great way to shut him down, as he generally builds very squishy. Don't build thornmail unless you already have one big health item, as it doesn't help too much against his q (and doesn't return its damage), and he will still kill you almost as quickly despite it. is your best friend against Yi.
Rammus - Think about it...
thnx guys hope it works never tried it yet but now i know it wont be that painful when palying agasint yi
