Take a look at the 
(check his items, he's not even building tanky) and look how I'm dealing NO damage to him for a few seconds. The only damage he takes at first are from his ult
https://i.gyazo.com/c98e864363b2918527c9e10420655658.png His build
My build https://i.gyazo.com/ab0cc8793e6f935e53d870e7a8c92fdd.png
whizkid752 votesHis Ult + his bonus MR passive + Phantom Dancer Passive (+12% dmg reduction) helps mitigate all your damage.
nuclearwarpotato1 votesIf you look he is actually taking damage. This isn't just from his ult, there are multiple instances of it and they all line up with your spells. You just aren't doing much damage to him is all it is and his crazy regeneration is healing him back from your damage very quickly.
Madsin251 votesMundo gets a butt load of MR from his W(E?). Combine that with you have zero magic pen and your gonna do nothing to him.
