Mundo's E is very, very bugged right now, and in a good way.

For those who aren't aware of how Mundo's E works, here's a refresher:

ACTIVE: For the next 5 seconds, Dr. Mundo's next basic attack has bonus range and deals a percentage of his maximum health as bonus physical damage.

On activation, Dr. Mundo gains bonus attack damage, increased by 1% per 1% of his missing health.

However, as of patch 6.14, Mundo's E is bugged, causing him to to pay E's health cost and gain the % max hp damage on every single auto for E's duration. Late game, this easily adds up to over 200 extra damage on every single auto. Alas, you also have to pay the health cost with each auto so it's too crippling to use early game.

But there's a twist: This bug only occurs if you cast another command during E's duration any time after the first auto but before the next auto. This means that, if you press E and then don't press anything else, this bug doesn't occur, meaning you can avoid the extra health cost and damage if you so choose. And Riot seems to have no idea this bug exists because they're said nothing about it, they haven't disabled Mundo, and there's no fix for this bug in 6.15.