The top champions outside of lane to counter Dr. Mundo include Tristana, Ezreal, and Kai'Sa. These champions are all great at countering Dr. Mundo with win rates over 56%. Even if these Dr. Mundo counter picks are not used in the same position as you, it's not smart to take him into any of these matchups. They will likely crush Dr. Mundo.
Yet, if the enemy team brings either Tristana or Rumble, you should seriously consider picking him, as he easily wins against these champs with win rates over 54% against each ofthem.
methods2.text1
methods2.text2
methods2.text3
otherMatchupsDescription