What champs mess you up?

What champs do you see during select that make you groan? For me it is pyke and darius! Their mere presence forces you to approach group fights differently. Darius, if he isn't killed or forced out of the fight early you will lose, pyke...idk what to do against pyke? Mf'er seems to be in urf mode by mid game and is untouchable if the player knows to rotate cds.

What champs force you to alter playstyle entirely?