Donaire, Trinidad & Julian Jackson. Maybe De La Hoya too, that left hook on Vargas was just something else. I still can’t believe how quick and short it was.
It's a rear hand. I think OP means left hook with front hand, in Pac's case, it would be right hook cause he's southpaw.
One particular left hook perfectly timed and executed that still sticks in my mind to this day from a good hooker is our 'enry's against Ali. That's gotta be up there with the best of them IMO. A more recent one that was devastatingly good (and satisfying) was Povetkin's against Whyte.