User blog comment:Commander Marko/Overpowered Champions that nobody considers OP./@comment-13536822-20130822131719

I can completely agree with you on Nasus and Xin Zhao, cause they really are ridiculous and I consider them some of the cheapest champion picks in the game, besides after rework Yi, can't be shut down Fizz, and completely destroys midlane Kassadin.

But anyway, I would add Kassadin, and not so much FIzz (though you could say playful/trickster is a bit toxic to any all skillshot champ) because he counters almost every mage in the game. Voidwalker is going to dodge any skillshot you throw at him, and gives him the strongest escape and chase in the game, not even mentioning the late game insane damage. By fielding him, you can completely shut down champs that need to be around to shut down the rest of your team, and since the only counters to Kass usually aren't played mid, good luck finding someone willing to play an unconventional champ.

You get the point. He's toxic in midlane.