There's only one type of corruption.
The more you lose to an enemy the higher your corruption with that enemy, making it harder to defeat that enemy. If corruption gets too high, that enemy becomes unbeatable.
There are 2 ways to remove corruption.
1: Go talk to a friendship 100 version of that enemy, and ask her to remove corruption.
2: Ask Meia. Since losing is what increases corruption you get help points. If an enemy's corruption is so high it's impossible to beat the enemy, you have to rely on meia to remove the corruption.
There's 1 way to reduce corruption.
Defeat the enemy. If you win while you have some corruption against the enemy, you'll remove some of it. If you continuously win against that enemy with some corruption you can remove all of it.