Miki

Background
Miki has no memory of her childhood, having been abducted at a young age by the infamous Frieza. Miki was used as a training dummy by Frieza. Frieza designated Miki as his favorite training dummy, as she was notably more durable than most of the beings Frieza abducted for this purpose. Miki fought Frieza many times, being beaten to near death many times, only to be healed and forced to fight again. Miki didn't simply allow herself to be constantly beaten, secretly studying Frieza and his techniques during their "sparring" sessions and practicing the same techniques in secret. During their final encounter, Miki surprised Friezia by using his signature Death Beam attack against him. Unfortunately for Miki, her version of the attack was significantly weaker than Frieza's. Frieza responded to Miki's surprise attack with a Death Beam of his own, blowing a clean hole through her abdomen. Thinking he had killed Miki, Frieza had her body ejected from his ship. Frieza's mistake was Miki's second chance.