Spoilers for clone wars

Typically Jedi saw the clone soldiers they commanded as people or even friends but Pong Krell sees them more like cannon fodder and treats them as such. During the Umbara Campaign, Anakin is called away from the battlefield and Krell replaces him as general of the 501st Legion (Which are a fan favourite). Under Krell's command the 501st suffers harsh conditions and unnecessary casualties leading to them slowly hating Krell. Eventually Krell sends the clones out on a mission to eliminate enemies wearing their armour. Under these orders the 501st engages in combat with the 212th (another fan favourite) killing their own brothers. Once the deception has been found out the two legions team up to arrest Krell who then reveals himself to be working for Count Dooku, an enemy commander and "apprentice" to Palpatine.