1) Having the quality of being badass enough to elicit a “what the fuck” response. The "what the fuck" is shortend to a simple and emphatic "the fuck" which is then inserted between the cheeks of "bad" and "ass."
Rarely used, it's only used when you're about to call someone a "fucker" but knowing that it's too inappropriate, and asshole would be something more appropriate, you compromise and mix the two.