"Fire Fist" Ace said and attacked cocking back his arm but Vash in quick steps got out of the way of stream of fire. A ship in the distance was destroyed by the flame, it was the ship of Baroque Works which housed grunts named 'billions'. There were six more ships like that that seemed to approach the harbour. Both combatant ignored the threat and started duking out in the air. Ace flew up using flame jets, and although using flames to fly was exhausting, he couldn't do anything to an opponent possessing flight ability like Vash. So Ace also turned up a notch and met Vash in midair clash.
Ace's whole body aflame started punching out fire fists, Vash dodged them with excellent maneuvers. The approaching billion ship's were destroyed in the crossfire between two dangerous fighters.
"Fire Gun" Ace pointed his index finger and middle finger taking an aim, he shot fire bullets to try and hit Vash. In retaliation, Vash kicked with tremendous power, hacking out a large air blade, it was simply too fast and Ace only managed to get out of the way in a nick. Ace sweated buckets seeing he was almost split in two.
"Phew... too close." Said Ace, although he was logia he felt threatened from the invisible element contained within the air blade. Ace became more cautious of his opponent. He turned up the heat and started throwing his best moves. Ace wanted to quickly decapitate Vash.
"Fire Fly... and Fiery Doll, with this go to hell you bastard." Shouted Ace, he created innumerable small fireballs around Vash, after that all the fireballs quickly ganged up on him like they were attracted to Vash.
"Hmm... at least you aren't a knucklehead. This technique is good, I'll give you an A- rating for that but..." Vash said, and his body rotated in weird way, he produced a hurricane like air blades, dispersing all the fireballs.
It was truly the first time for Straw Hats to witness a battle of such level, they were shivering from the excitement and also worried for the beating they would receive, if Ace couldn't repel the flying devil. They didn't even cheer for Ace from the fear of Vash.
These two people had been fighting for quarter of an hour, and during this time all the Baroque Works ships were destroyed, either in blazing flame or through countless air blades.
"haah... are you out of fuel cause I ain't feeling the heat." Said Vash in taunting manner. He looked fresh not even tired from the intense fight. He mocked Ace like he was getting sleepy from a boring contest.
"Damnit, stay still bastard." Ace was annoyed that each of his technique was countered so easily by Vash.
"Flame Lance, haaaa...." Ace created two pole like construct from his flame, he launched both at the same time trying to predict and outmaneuver his opponent. After throwing flame lances which Vash easily dodged, Ace threw another two of such attacks in quick succession, like that he threw total of seven flame lance.
"Explode!!!! Seven Pillars of flame." Ace said in loud voice as all the Flame Lances quickly grew in size and exploded. The sky became red from the heat as if a world burning flame dragon was wantonly breathing fire. And although Vash had been dodging those spear like flame, he was thrown back some distance in the air from the remaining shockwave from the blasts.
"You are good kid, you've got a lot of spunk. For that move I'll give you an A+ rating. And I tell you, if it wasn't me as your opponent, the person facing you would be incinerated to dust." Vash said smiling, his sleeves burning as he put out the fire by some casual thumping.
Ace was out of breath. As devil fruits ability most of the time would consume stamina, and Ace's recent technique just used a lot of it. Ace got back on the ship deck of Straw Hats. He started preparing his ultimate move. Ace again floated up and massive amount of fire generated around him, after some time, all the flames gathered together in front of Ace's outstretched palm as a massive fireball came into being.
"I'll admit defeat if you can take this move and survive. Great Flame Commandment: Flame Emperor!!!!" Said Ace as he launched the massive ball of fire to the position of Vash. It looked like a miniature sun packing intense heat. Vash could have easily dodged it, but it was too much close to the surface, and it would burn down half the city of Nanohana if it exploded near the docks so he swiftly came before the ball of fire, intending to meet it head on.
"Front Kick!!!" Said Vash in loud voice as he kicked with such speed that the air stagnated for a moment. Vash's foot was covered with lightening like glow and it sent the fireball away upward where it exploded in a bright shine. It was like a star had bursted ending its lifespan. At this time, all the people in Alabasta Kingdom felt the rise in temperature, they looked up to the source of it and saw a red burning entity beside a white sun. It was surreal sight for the people in Sandy Island as this island was already warm enough from the single sun, they started praying to gods to let them off from the torture. Their prayers became reality when the red burning ball of fire slowly disappeared after sometime.
"Phew, that was close. People would have died unnecessarily." Said Vash. At this time at the dock, Straw Hats and other bystanders were shocked beyond belief. They started thanking Vash from saving them from certain death. But Vash was really angry at Ace for recklessly releasing such a move that could easily level a town. He got behind tired Ace and pummeled him harshly. Ace's head and face were swollen from the beating. Vash also didn't let off straw hats as he also beat them up in flash. All the people on Going Merry were sporting bruises and bumps on their bodies with Ace being unconscious.
"Well... that was refreshing and it will teach you not cause trouble needlessly." Said Vash who flew back to the town.
"uwaaah... woooo....." Usopp could only cry in pain.