Let's resume the situation
We have
> King / Queen aim at killing the scabbards at all cost, yet they think they can't do that due to Marco taking too much of their attention(according to King despite having Queen alongside him)
> Marco is fighting King and Queen in a 2 vs 1 for multiple chapters(with his healing ability active on the dying samurai he aims at protecting), yet Marco only has a scrath, while King is dripping blood, with Queen even more damaged
This suggest it'd take much more time to see a winner despite Marco already fighting in a 2 vs 1, likely the reason of Perospero's involvement by the end of the chapter. He'd play the role Flampe did in the Luffy vs Katakuri fight, except that unlike Katakuri who was getting stressed on base Luffy without noticing Flampe, Marco would be facing 2 opponents with higher bounty than Katakuri, with Perospero's potential support being superior to Flampe's as well
If Oda goes out of his way not only to portray Marco in a comparative level to the 2 strongest calamities despite fighting in a 2vs1 to the point of involving Perospero's help to tip the scale of the fight, that alone suggest than in case of a 1 on 1, Marco would have ragdolled them
He is a level above King