Whitebeard was sick, but I don't know how to quantify that. He was still considered the "strongest man" and an almost unstoppable force at Marineford.
I tried to avoid cases like that, or surprise attacks like Jozu hitting Aokiji and vice-versa, etc.
Also I didn't included examples that depends only on how Devil Fruits works such as Akainu killing Ace.
Not exactly. The Gorosei mentioned Marco as one of the forces that could stop Blackbeard. It wouldn't necessarily take an Emperor or Admiral to confront Blackbeard.
I didn't included Rayleigh as a Commander because the hierarchy of the Roger Pirates is not clear. All the Emperors had Commanders, Executives, etc.
In the end it was decided in a duel. Nonetheless, there never was much difference between Akainu and the others.
Well, it is difficult to quantify how much weaker whiteboard got, but we do have statements and panels that give clues. For instance, WB was stabbed by square, we were told by his crew that attack should never have hit, he should see even surprise attacks from allies coming and be able to defend, it sounds like he was so sick that has a halo was failing him, which makes sense.
We know he also has conquers haki, but couldn't use it, we know he used his bisento to stab admirals and they managed to survive, this could be them using haki to know how to manipulate their logia bodies similar to katakuri and his mochi fruit. There were also scenes where he didn't have the strength to do things when he wanted. We know he was very sick, we know the sickness was bad enough that he was having trouble with using halo, and his overall abilities weakened enough to give Marco, who's been with him for decades, pause, and make him wish whiteboard was just a couple years younger. This suggests that the WB who beat ace up continuously was much stronger than his marineford counterpart, which makes sense as two years before he could stop ace in his sleep, and at the war he was stabbed right in the front by squard.
Whitebeard was weakend to the point that all his physical abilities and at least two of his types of haki were impaired, and even with having lower physical and haki abilities, and after being stabbed through the chest, he was still able to go toe to toe with akainu and kizaru and hundreds if not thousands of other top marines, and still have the power to do some damage to blackbeard after the fight for ace.
As for commanders, their strength varies a lot, but at marineford, marco and jozu were going head to head with admirals, but we're distracted watching WB and for caught bad with freezing and lasers. It seems like commanders powers, like the shichibukai, vary greatly, and are hard to quantify, commanders could be on par with the weaker shichibukai, like curiel of the WB pirates against moria, or they could be strong enough to compete against an admiral, like marco.
The WB war showed us one thing, that a very weakened yonko missing two of his top fighters nearly defeated the gathering of marines and the 5 shichibukai with them. If it happened before when whitebeard was 2 years younger and Ace and Thatch were there? With jinbei and crocodile still as warlords? Hancock would have not shown up, jinbei would be in impel down, so instead of 5 warlords and the strongest marines against a weakened yonko missing two of his top fighters, it would be 5 warlords and the strongest marines against a less weakened yonko with all his commanders. He might still have lost, but who knows?
