Dr. Mundo Build
Killer Mundo is an idea to make Mundo a little bit more interesting and attractive. Without losing a lot of survivability mundo can " carry " at least as long as his lane is considered, and focus while on a teamfight more effectively. However there are a few counters for this build that need a lot of caution. In order to get it smooth you need to clear the waves and attack straightly to your opponent. Enemy ganks are now easier so try using wards. A damaging Mundo is a bitter surprise for the enemy who is preoccupied by the idea of a tanky opponent!
Maxing Q is what makes Killer Mundo terrifying so go on and do it! As for E it would be wise to max it in order to push more and sustain lane control. However if enemy ganks are very often then Maxing W 2nd will protect mundo and give him the ability for easy kills on the hardtriers that will chase him back to his turret! The ult is the ult... Use it either as utility in order to keep pushing when hp is running low or while in a fight or when you go after someone!
The item set is very specific as it aims to a Mundo that can harm whoever stands against him and be able to survive during the various phases of the game! Feel free to change the order if you think that's necessary for the specific game!
Creeping / Jungling
Killer Mundo is a useless freak in jungle cause he gets killed by the mobs way too easily... As for creeping I believe it's necessary in order to buy this expensive build. However the build itself helps creeping as it gives more power to the E-W skill combo in order to damage minions ( E) and take last hits (W). Apart from your cs clearing waves is significant as mentioned before!
Killer Mundo is not the standard tank type that will be full of assists after a teamfight. Although he is easier for the enemies to focus, his massive damage usually splits them in a teamfight and make it easier for him to focus their adc or apc. Mundo's W combined with one of the offensive masteries weakens all the enemies around him and armor reduction by Black Cleaver comes on top to finish their defenses. Liandry's Torment makes enemies suffer even at a safe distance from mundo and the other team causing them to flee even farther.
Killer Mundo is a funny Mundo that can split push easily, focus easily, get easy kills and dominate teamfights deciding which enemy dies who flees who stays and who gets focused. BUT in order to achieve these you haveto be very careful against crowdcontroling enemies and be pretty skillful with the cleaver which will do all the work for you in the early game! HAVE FUN!!!