Teenage Mutant Ninja Turtles, Season 2

Leonardo:
I don't understand how you can serve someone as evil and dishonorable as the Shredder.

Karai:
You knew the Shredder only as a merciless enemy, but I knew another side of him. [flashback starts in Japan] It was he who discovered me many years ago in Japan after my parents had abandoned me. He took me into his home. He allowed me to train alongside him, and thus I learned the ancient art of ninjitsu. I respected him and he trusted me. To me, he was Oroku Saki. He was more than just my master, he became... my father. [flashback ends] It was his destiny to find me, and it became my duty to serve him, as it became your fate to slay him. Thus we are all servants of Fate.

Leo:
I'm not so sure. Master Splinter says we are free to choose our own path, that our lives are dictated by our choices.