If your character’s starting off at level one, they’re really only getting started with adventuring. You can let that be reflected in their backstory.
If you want to play a badass, starting above level 1 is allowed, though probably not recommended for new players still learning the rules of whatever system you’re playing.
That’d do it. White Wolf’s Scion will do it too. Or Eclipse Phase…, really, there’s a lot of systems where you start off as a badass.
None of those systems we’ve named have levels, though.