A crocodile doesn't take orders or payment. It simply exists as part of its cycle, and is as likely to be killed by the hippo as it is to kill the cow.
Killing ate away at my soul. I wasn't born into it like most of the Order, so my perspectives a little different. But that said, you shouldn't feel shame for having the skills you do. Existing in the world outside the League though, those skills are put to different uses.
The question really is what do you want? Do you want to be an assassin or is it just the option because that's what you're good at? I'm really good at knocking people's heads in. But I found I'm happier when I'm doing it to protect people over someone ordering me to.