It has a good meaning! It means "cool" combined with "tough" in a certain way... It's a bit hard to describe XD Usually we would say that action movie heroes or video game characters are badass!

As Tessa said, it's more so a combination of tough and cool. Some people would use the term to describe someone who just won a fight: "Wow, you're such a badass!" It can also be used ironically. For example, if somebody were trying to brag about doing well on an easy test, someone might say: "Wow, what a badass" with a sarcastic tone, as to imply humor and that they're overstating their actions.

something rebel or when someone who is tricking other people, if some one screws you, you can say to him :you are such a badass....

like a person who is rude and does not care about what other people says to do what he wants

someone that you do not mess around with/make fun of/steal from because he/she will beat you/hurt you