First place must be Control Priest. I know it is irreplaceable class identity at this point but it is firmly not fun to fight a deck that has copying (or even stealing) your own cards as a win condition, and besides that does not much but drawing cards and clearing the board two dozen times. If I play any kind of control deck I concede right there because it is an auto loss against my own stuff.

I also hate playing against enrage warrior, getting killed in two turns by a 30 attack remornia feels unavoidable.