Who is the character that's made such an impression on you as a badass, you know you'll never forget just how cool they are for as long as you shall live? Show us a video of the character you are talking about. Preferably a video actually showing the character you nominate doing what you consider to make him or her badass worthy material.
My choice is .hack//GU's Haseo. Even though he has plenty of videos showcasing his awesome combat skills, that's not what I think about when I first think of his status as a badass. It's his "In Your Face" attitude that defines him for me.