Clone Wars and Rebels because tbh I couldn't care less about his character beforehand. I only remembered him as the sith with 2 lines of dialogue that killed one of my favorite jedi in the prequal era. His animated appearances really fleshed out his character and I honestly felt some kind of empathy for him.

The Clone Wars and Rebels is by far my favorite appearance for him

The original appearance as that’s what set the character in stone as one of the most iconic things from the prequels that’s positively looked at. Ray Park blowing everyone’s mind in 1999 made that character truly impossible to kill off lol