Hyenas are absolutely vicious and are very powerful for their size. They're hardly small either, as a large female can get to be upwards of 160 lbs.
Male lions are basically the only animals that ever **** with hyenas. Neither Tyson nor Brock Lesnar are male lions. Hyenas are built far sturdier than humans. It's not going to go down with a few punches. On the other hand, it would only take one leg bite to incapacitate either of them. Hell, Lesnar can't even take a punch.