But I'm a boy, I can't have a girl avatar
I'm a guy. I use female avatars. My past ones are olivier armstrong from FMA, lady gaga in a pink outfit, an ironic parody of that image made by myself, and more recently toph beifong from avatar.
But then again I'm a feminine gay dude so I may be a bit biased.
I've never really understood the need to preserve one's masculinity since I've never really been masculine myself. Heck I play most games using a female character rather than a male one. Femshep forever!
But if you're against using female avatars, use a male one! There's plenty of badass male characters in anime. Ones I'd suggest are colonel Roy Mustang or major Alex Louise Armstrong from fullmetal alchemest, light yagami, L, or Near from Death Note, prince zuke, general iroh, or firelord ozai from Avatar, or pretty much any character from any anime you like. I'm currently using the most badass female character from whichever series I'm currently watching through (this is my third time watching through the last airbender) but yeah. Find a character you like from a series you like and use it!
On the subject of avatar not being an actual anime: that's BS. It being based on the region it's made in is entirely ridiculous. The title should be based on the work itself not the place the work was produced in. Art style, themes, storytelling philosophies, culture. I know nobody actually said anything about that here, but I know there's debate about it.