With DMP, triforce, Swiftness boots, alacrity, and rylais...

Mordekaiser is basically a reasonably fast wall of cc and doom, not someone who is super easily kited. He lands his ult on you? boom, permaslow, and then he runs at you with all of his speed bonuses and 4khp and shits on you with q.

And this is coming from someone who plays him...