Edward Newgate in his prime, the Strongest Man in the World.

VS.

Kaidou, King of the Beasts and the Strongest Creature in the World.

IMO Whitebeard takes this highly extreme diff, but I honestly believe that it could go either way.

Kaidou showed incredible levels of durability and strength during the Onigashima Raid.

(All these moments are onlu showcasing the fights between Kaidou and Luffy, but the also fought the Scabbards, took attacks from the other members of the Supernova alliance and also fought agains Yamato).

I personally believe that Kaidou has higher physical/brute strength.

Whitebeard posses a more powerful Devil Fruit, but both have insane control of their powers and abilities, having become masters in the use of their DFs and Haki.

In the end it would come down to who has a better Haki.

Considering that Whitebeard was one of Roger’s few equals, I’d believe that he’d win this one.

Again, it’s a highly extreme diff for him.

Kaidou proved to be one of the best fighters in the verse, being able to get stronger when drinking sake, as he would “unlock” different forms of combat. Perharps if he could sustain these forms (like the “Murderous Drunk”) for longer he would win, as his physical abilities become greater.

After all, there ocasions when a greater physical strength overcame a better haki.

In this case Big Mom was in her “Olin form”, so she wasn’t using haki at all while Luffy was using Ryou. And in Amazon Lilly, Luffy defeated Honcock sister, they had armament and observation haki but were both outclassed by his Gear 2.

Hugs from Garp.