Orphaned at an unidentified age, Millia ends up forced into the Assassin's Guild and unwillingly becomes the host of the Forbidden Beast Angra. Though she tries to kill herself many times and falls into a toxic relationship with a fellow assassin, she decides to take her life back, even if it means living on the run.
Angra has bonded with Millia's hair and imbued it with immense strength, along with allowing it be shaped at will. As such, it has become a versatile weapon in the hands of the ex-assassin. It is also capable of giving off a gold glow, similarly to the magical locks of Tangled's Rapunzel. Then again, Millia isn't exactly healing people with hers.
Typically dubbed "cute," though recognized as powerful, Millia is by far the least sexualized of the characters on this list. And the last one had blue skin. Let that sink in for a moment.