Was it Earnie Shavers? Was it George Foreman? Was it David Tua? Was it Mike Tyson? Was it Gerry Cooney? Was it Smokin Joe Fraizier? Was it Tommy Morrison? People dont often mention earnie shavers or george foreman when this topic comes up but I dont see why not since they are perhaps two of the hardest hitters of all time and their left hooks are no exception. A hook from Foreman is superior to a hook from Smokin Joe yet Joe comes up alot more than george when people discuss who had the hardest left hook ever!
People talk about Joe Frazier's hook more because it was a better punch than Foreman's, even if you think Foreman's was harder. Who knows. I would guess Cooney or Tyson. Power is a hard thing to compare - are we talking about the hardest hook they EVER landed or their capability to throw consistently hard hooks. It's a difficult question to answer with any accuracy and will inevitably come down to subjective opinion.
That left hook bomb that Patterson regained the title from Ingo with could have taken anybody's head off IMO.
I'd go with Tua, but it's really hard to compare, cuz most of them used the punch on different opponents with different abilities to take a punch.
For sheer power it'd probably be Tua or Cooney. For all around better punch it'd be Frazier or Tyson.
Ruddock his best punch was "the smash" which was a uppercut/hook hybrid. But I don't think you meant that one.