Though those are good points the way I see it regarding Big Mom is she either:
- Went all out against Kid & Law and was trying to take them out by the end of the fight and lost the fight due to plot/circumstance
- Went all out against Kid & Law but due to her childish demeanor she did not perform as well as her body would have allowed and lost the fight due to that + plot/circumstance
- Did not go all out against Kid & Law at any point and lost lost the fight due to that + plot/circumstance
I think the second is the most believable based on how Big Mom is portrayed during Wano but the first could also fit. The third option I have a hard time buying since Big Mom on multiple occasions complained about Kid & Law not going down, was shown to put in effort to attack, took hits with lots of pain enough to even sacrifice years of her own life. I can completely say she lost due to plot but to say she wasn't seriously trying to take Kid & Law out in that fight doesn't seem supported by the manga.
Not saying she wasn't trying, but there's a lax approach to fights.
- Shanks is really the only Emperor so far who seems quick to anger and more so in context.
More so, look at the circumstances too where Kid was using his most powerful attack and Shanks saw that he had to end that fight there and then because his comrades would die.
The level of urgency is critically different to how Big Mom and Kaido pretty much always viewed the supernova literally throughout the battle.
Also, look at Kaido's strongest attacks:
- When Luffy died whilst in G4, we could have argued that was Kaido's strongest attack at that point, yet he only used what was needed for Gear 4th.
- He used a completely different level of attack against Luffy in Gear 5.
If Kaido had used his final attacks for G4 or G5 earlier on in the fight, the Supernova would all be dead for sure. Irony is we never really saw Big Mom's strongest attack because she was pretty much tanking and she got taken out at a moment where she never saw it coming - she fell into a hole pretty much and couldn't call her Homies.
The Emperors are seemingly so confident the output they give is only just slightly above equal proportion to the threat.
I think if Big Mom or Kaido wanted to defeat the Supernova at any point prior to their defeats, they would have. They just prolonged the battle unnecessarily.
Comparisons taken out of what is not in context to me... could have me state that since Shanks didn't defeat Kaido pre-skip when he tried to go to Marineford.... Luffy is therefore superior to Shanks since he defeated an opponent Shanks didn't.
I wouldn't believe that for one second, I think it's just circumstances that differ, Shanks just wanted to stop Kaido's advances as opposed to defeating him like Luffy who needed to do so.
And in regard to Big Mom against Kid/Law, she underestimated them, she didn't see them as that much of a threat like Shanks did and we saw Kid's strongest attack didn't have that much of an impact because she literally told Kid that once his strongest attacked stopped tickling (understatement ofc) her as all it really did was pin her down, they either give 50 years of their life or pretty much die.... this was in chapter 1040. Others watching said the attack wasn't affecting her much.
Only reason they won was the hole, the explosion and the volcano.
Big Mom really didn't view them as much of a threat as Shanks did who knew he had to take him out there due to the danger that posed to his crew... Big Mom never really had an instance where she used her strongest attack or tried to end the fight there and then.
No Emperor is outstanding, and if Oda really wants to make out Shanks as in league of his own, he would say he was the closest to the throne, he'd say he is the strongest Emperor, his rivalry with Mihawk wouldn't question his hierarchy in strength which it does, and Blackbeard would not have scarred him since scars in One Piece when they ACHE specifically imply they were defeated if you look at every character in series who has mentioned a scar they had that ached.
There's too many question marks for Shanks to be remotely claimed as the strongest.
I think he may be Luffy's strongest opponent, but I personally don't think he's Roger's equal until it's specifically stated. Roger stood above all and even stood above Whitebeard, no one even stood in league with Whitebeard while he was alive which for me completely dismisses Shanks' standing.