I recently read an interview with Donald Brashear describing what it was like to take on Joey Kocur in a fight:
Too scary indeed. Joe's punching power is legendary. He was regarded as being the hardest puncher of them all. When he caught someone with that right sledgehammer, it was lights out.
What Brashear learned that day was what many others learned on many other days: Don't mess with Joe Kocur. Don Jackson tried it, and had his jaw broken by a single punch. Big Jim Kyte took him on, then had to be helped off the ice. Brad Dalgarno got worst, though, when he had his orbital bone crushed. Dalgarno underwent several operations and missed over a year of action.
Here's the full Joey Kocur biography.