Vista has tremendous physical strength as he is able to match against Dracule Mihawk, who is known as the strongest swordsman in the world.
Vista has extraordinary mastery in dual wielding swordsmanship and even Mihawk acknowledges his skills. He even managed to deflect Mihawk’s flying slash attack which is powerful enough to cut through battleships.
So we straight up see him clashing equally with Mihawk several times, but we can’t realy tell if Mihawk is holding back or not. I still say that this guy is extremely strong simply because Mihawk knows him without ever fighting him, so it means he recognizes that he’s a swordsman and would pose a challange somewhat.
Another indication of his strength is that during the Battle of Marineford, despite having fought against individual Shichibukai and admirals as well as numerous Marine officers, he sustained no significant injuries.
PORTGAS D. ACE
Ace was strong enough to be acknowledged by the Yonko Shanks and Blackbeard, with the former saying he had earned his spot as Whitebeard’s second division commander. It was revealed that Ace received an invitation to join the Shichibukai at 17 years old!
Ace demonstrated his strength during his battle with Blackbeard: he was able to take Blackbeard’s punches, which were so powerful that the first made Ace cough up blood and the second nearly broke his neck, and retaliate quickly afterwards. Oda skipped a couple of parts of the fight but those two were destroying the island bit by bit. Van Augur noted that, as expected of the Whitebeard Pirates 2nd Division Commander, Ace’s basic combat skills were quite formidable even without his Devil Fruit powers.
Ace fought equally with Jinbe for 5 days which is extremely physically overwhelming, showing Ace has incredible levels of stamina, only top tiers have been shown to fight for days e.g. Admirals, Shanks, Mihawk etc even Luffy’s longest battle has only been 12 hours or so.
It’s been revealed through the Ace novels that Ace could use Armament Haki, which he awakened mid-fight against a vice admiral and it was STRONGER than the vice admiral’s own haki.
Ace’s Haki had been described by Shanks and Benn Beckman to be fiery in nature, to the point that Ace’s very presence was able to stop blizzards on an island for as long as he was there. As such, when he turned up on Drum Island, no snow fell at all on the island for an entire day.
I haven’t seen any other Yonko Commander that’s as impressive as these dudes. If there’s anyone who shouldn’t be underestimated, it should be these guys right here.
Ace was at least as talented as Luffy and he had the potential to become the Pirate King.
Marco would probably outlast every Yonko Commander, Jozu would probably overpower every Yonko Commander, and Vista maybe the same.