I don't like when people mention the game events. I prefer to have a backstory for the character and develop him like I see fit throughout the game. I hate when I see something like "the events of Helgen changed him and he now spends his life hunting bandits and protecting the innocent"
Eh that's worse than being the worst. Who wants to be the world's most mediocre assassin? I lied, that could be a fun play through as well. An assassin who hates his job so he just goes around half ass assassinating people. To lazy to care if he is caught or seen, collects his paycheck, and then goes home to catch crap from is wife and kids.
...He/she was a poor farmer until ??? killed his/her livestock and suddenly decided that he/she would become the most badass of badasses. Oh, and now he/she wants revenge on ??? group for slaughtering his/her farm animals.
OR
...He/she is a lone wolf (or vampire), the last of his/her kind that stalks the chickens of the hamlets of Skyrim stealing their souls and shouting some hot breath on those that would protect the Rooster overlord!