Unkillable Mundo

Mundo is unkillable. While playing with friends we encountered a mundo top who was pretty good, however he would not die! It became very difficult to kill him he even went through a third tier tower against four of my team (which weren't doing too bad) and me who was doing pretty good, and still didn't die, moments later he was back at full health. I ask riot to please nerf mundo if not his health or damage then at least nerf his movement speed and ability to escape almost any situation by literally just walking away it is not fun, unbalanced and honestly a very bad time when playing against something such as that please riot nerf mundo in some way.