Pipino Cuevas merits consideration. He coldcocked Harold Volbrecht with 1 punch but was more well known for his bone-crushing punches which broke facial bones in Angel Espada, Billy Backus & Harold Weston. Pete Ranzany was KO'd by both Cuevas & Sugar Ray Leonard and said Cuevas was by far the harder puncher. Clyde Gray & Weston fought both Cuevas & Hearns and both stated Cuevas was the harder puncher. Randy Shields fought Cuevas, Hearns and Leonard and did say Hearns punched hardest but Pipino hurt his left hand in his fight with Shields and couldn't deliver his best power punch. Pipino wasn't that skilled a fighter but was a devastating puncher.
Another fine mention. For a short time when Hearns had his hand troubles Spinks was the best puncher in boxing.
Not sure why he hasn't been mentioned, maybe I'm missing something, but Langford KO'd more fighters than Foreman and Tyson combined and he often fought guys 20-40 lbs heavier than him. He at least deserves a mention.
Pipino Cuevas is my choice as well. The combined won-loss records of vaquished opponents in title matches during his four year reign of terror was a freakish 505-70-29. Every punch he threw was an intended knockout blow, and against the defensively gifted Randy Shields, he secured his 15 round credentials as well. Hearns was fortunate to have been born with the endowments of height, reach and speed which allowed him to hit Cuevas without getting hit in return. The definitive leverage puncher, it's very well known that he's the only boxer besides Foreman to break the speed bag at Gleason's Gym. He fractured bones like Fitzsimmons, but while Fitz did it with two ounce gloves, Cuevas did it with eight ounce gloves. If he'd been 6'4" and weighed 220, he might still be champion. Anybody who watched Pipino's four year tltle run might be hard pressed to name another better candidate for this distinction.
It's nice to see some credit given both where it's due and where we don't usually find it. What a fantastic asset you've been already.