Just a warning, there are spoilers about Mirai Nikki!!! (Mainly in the last picture)
In my opinion, one of the most kick-ass females in anime is Uryūū Minene aka 9th! She starts in the show as a terrorist trying to kill Yuki and Yuno, going as far as blowing up their school, and ends up getting stabbed in the eye. THIS GIRL GOT STABBED IN EYE, HAD IT GOUGED OUT, AND SHE STILL FIGHTS. This is no ordinary girl everyone! She even teams up with Yuki and helps him making her an even more badass character! And if you mess with Nishijima, it's over for you. I sure as hell would hate to be her enemy!