one hell of a (something or someone)
1. An exceptionally good, exciting, or interesting thing or person. Marty sure is one hell of a guy, always willing to lend his friends a hand! Two cars for the price of one? That's one hell of a deal!
2. An exceptionally bad or difficult thing, activity, or person. This is one hell of a math assignment—I can't understand the first thing about it! Boy, that is one hell of a haircut. You're going to go out in public like that?