Because you like Optimus Prime in Transformers
The only thing standing between Rocky Balboa and glory is the person facing him in the boxing ring. See them in Rocky Series.
For Kazuya Mishima, the power of the Devil is now his and his alone. See them in Tekken .
Wei Shen is an undercover cop on a mission for justice (or at least vengeance). See them in Sleeping Dogs.
Her interests include martial arts, interrogation, and hacking. Natasha Romanoff is the ultimate spy. See them in Marvel Cinematic Universe.
Dominic Toretto lives his life "a quarter mile at a time", and he burns through those miles faster than anyone. See them in The Fast and the Furious.
Told her son will one day save the world, Sarah Connor dedicates her life to training him to do just that. See them in The Terminator.
There's no obstacle too great for this charismatic treasure-hunter. See them in Uncharted.
Xena's a warrior on a redemptive quest who excels in extreme sports and uses a whip to block axes in mid-air. See them in Xena Warrior Princess.
Ethan Hunt's mission, should he chose to accept it, is to save the world from impossible threats. See them in Mission: Impossible.
His superiority complex coupled with his bitter desire for revenge makes Vegeta a formidable foe. See them in Dragon Ball Z.