Have you seen or heard of an exampleof a fictional character that is good but has acted as the evil person for example to help the good guy win in any sort of media?
Could you provide and example as well that would be great ! :)
Most Helpful Girl
the 100, one of the characters who fell in love with the main character murdered someone who he (wrongly) thought kidnapped her. it was for love but he killed someone innocent even if he's otherwise a good person.
Most Helpful Guy
The Punisher Marvel Comics (though he actually DOES do some pretty sadistic and pretty evil things)
Saitama from One Punch Man.
Itachi from Naruto.