Dragon Ball Z: Supersonic Warriors/Android 18

Android 18 and Android 17 were normal humans until they were kidnapped and altered by Dr. Gero, turning them into Androids. They're quick to rebel at the beginning of their story and end up killing the scientist. Android 18 usually always has her brother by her side, though he isn't playable. Her goal throughout the story is to face Goku, who is supposedly the toughest of all the Saiyans.