I haven't had a problem with yi until now.
In the last teamfight of my most recent game, the enemy yi got cc'ed by veigar stun and morg q. But we couldn't burst him because he had around 4k health and two mr items. After the cc was over, he proceeded to q and wipe 3 of our squishies immediately and then ran at me with 50% of his health remaining. I q'ed him, got both sides to hit, auto+red smited him and kited backwards autoing more. He had 1/10th of his health left and then w'ed as my ulti was going to him, lives somehow and then proceeds to q me and instagib my entire healthbar in two autos then ends the game because of 50 second death timers. There was absolutely no counterplay to what he was doing. CC didn't work, raw damage did not work. Blowing everything on him did not work. So I sat back and watched myself lose a game that should not have been lost simply because of the sheer power of 1 champion.
He basically 1v9ed the game doing more damage than any champion in the lobby, while simultaneously being the tankiest person in the game. I'll admit when i've been outplayed but wow, I just felt cheated after experiencing that. I felt like we outplayed him in every way and he still got to ace our team for free.
The best part was his comments after the game, as shown above. He tried to pretend like he outplayed us and acted like there was counterplay to his champion. If there was counterplay, we did it. It did not work.
That was the single most unbalanced thing I've ever seen in my 1000+ games of league of legends. I have never seen anything come close to the level of bs that sated guinsoos tank yi is.