Byrd was my first thought too but he's just not a light heavyweight for the same reason that rocky marciano isn't.
Byrd had an iron chin. He took punches from Wladimir who hit harder than Liston and Foreman. Neither Liston nor Foreman were explosively quick. Byrd would be much more troubled by combination punching, see Ibeabuchi.
Many have mentioned Charles & Moore, they are the 2 that sprung immediately to mind for me. Slight chances to both.
Byrd stayed on the ropes for too long, but he could dodge punches if thrown one and twos at a time. Ibeabuchi kept throwing and Byrd ate an uppercut.
Ike was mostly just plodding after him, he wasn't throwing combinations in the round he caught him. He wasn't cutting the ring either, Byrd lazed on the ropes by choice and got caught with a single looping punch out of the blue. Ike had thrown quite a few haymakers throughout the bout and he finally connected clean and that was pretty much all she wrote. Liston and Foreman both have a more educated offense and it's highly likely he suffers a similar fate. One punch was all it took to start the irreversible slide. Liston would set him up more off the jab than Ike did.
You named two fighters..... of which footage is only available for one of their fights..... and it was the GOAT against an injured and aging Liston. Strong argument there pal. A prime Dempsey didn't hit anywhere near as hard as Liston and Foreman..... let alone a faded version of Dempsey. Are you honestly going to dispute this?
Ah but he was stopped by Wlad,no shame in that,Klitschko younger was a monster puncher.However I'm very doubtful that Wlad punched harder than Sonny or Big George. As for speed of punch well I wouldn't say Ibeabuchi was quicker than either a prime Liston or Foreman.
Why do you believe Liston and Foreman punched harder than Wladimir? Half of Liston's opponents would not even qualify as HWs in Wladimir's era. Klitschko laid out much bigger and durable men.
Foreman got fooled by rope-a-dope. He was very slow and telegraphed his punches. Watch him wing his punches against Young. Byrd is more durable than most HWs in Liston's era, and he is a southpaw.