As a Diana main, it's hands down Mordekaiser. So glad there are literally 12 Mordekaiser players in NA. you poke out Iron Man with Crescent Strike over and over again, and when you finally poke him down enough, you try and burst him down but he refreshes his passive shield while getting hit with Qs with no escape. Then he turns you into a ghost and watch as your ghost takes down your turret at the speed of light. You literally are required to laneswap.