The fight itself almost takes a back seat to the notion of the villain facing even the slimmest prospect of comeuppance. What if, perchance, that retribution never came? What if 10 of the most cherished One Piece heroes, that so swiftly dole out the humble pie, were reimagined as villains themselves?
10 Monkey D. Garp
Venerated as the hero of the Marines, Monkey D. Garp has a resolute grasp of justice that extends beyond pirates and even towards his peers within the illustrious Navy. However, what if that same scrutinizing eye wasn't attuned to altruism and instead focused on barbarism?
Garp's monstrous strength and Haki, if tempered with a malevolent nature, could have easily exceeded the villainy of Akainu. If left unchecked, Garp could've been the most tyrannical Fleet Admiral, after murdering his friend Sengoku to claim the lofty position.
9 Princess Shirahoshi
Equipped with planet ending powers and a tragic backstory, sufficient enough to stoke the flames of vengeance, the Straw Hats are incredibly lucky that Princess Shirahoshi is on the side of the angels. Even if stripped of her abilities, Shirahoshi's towering stature could present a problem by way the titanic power her blows could muster.
Also, commanding the whole army of Fishman Island could even spell devastation for the World Government. Luffy may not enjoy Princess' Shirahoshi's constant blubbering, but it handily beats the alternative.
8 Rayleigh
Known as the Dark King, it's odd that Rayleigh is as affable as he is. If he were to behave in a manner befitting his moniker, Rayleigh could upend the world of One Piece even at his current age.
Heightening the danger he presents outside of his physical prowess, Rayleigh is also one of the few people that knows the exact location of the One Piece. If the treasure is a weapon, as many theorize that it is, Rayleigh would have unrestrained access to it.
7 Whitebeard
Given that fans' interaction with Whitebeard is limited, there's hardly enough information to discern that he was as gentle a giant as he appeared to be in his elder years.
However, there's no doubt that if the pirate known as "the strongest man in the world" dedicated himself to villainy, it would take a full-fledged war to stop him. Causing indiscriminate earthquakes for fun and wielding a mammoth fleet, Whitebeard could have the advantage in any naval battle. Luffy would've had his hands full.
6 Law
As a skilled tactician, Law already owns a host of traits that would make him a savage opponent for the Straw Hats. If he decided to break bad, Law's Ope-Ope no mi alone might be enough to undermine Luffy and his crew.
Imagine how much havoc Law could wreak on the Thousand Sunny if he implanted the monster trio-Luffy, Zoro, and Sanji- into the bodies of the coward trio- Nami, Usopp, and Chopper. The battle tilts further in Law's favor if you add his crew.
5 Zoro
Even under the banner of the Straw Hats, Zoro's bloodlust runs rampant. If allowed to stray into the wilds of villainy, Zoro could be the greatest foe to ever confront Luffy.
In every battle, that we've seen unfold between the two, Luffy and Zoro have equivalent levels of strength, but, with the bonds of comradery severed, Zoro might have the advantage. Driven to the point of obsession, Zoro's dedication to gaining sword mastery would be his sole focus if he left the Straw Hat crew.
4 Dorry and Brogy
Although introduced relatively early in the story, Dorry and Brogy are still giants, making them threats on whichever side of the Grandline one resides.
Much of Elbaf, the home of the giants is shrouded in mystery, but Dorry and Brogy's legendary status has been solidified throughout the story by other giants of strength and repute. If the duo were to reunite with their old crew of giants, armed with malicious intent, Dorry and Brogy could siege every inch of the One Piece world with ease.
3 Portgas D. Ace
Long time One Piece fans will remember how ominous and imposing Ace's introduction was in the Drum Island arc. Initially clad in black, fans speculated on Ace's allegiances only for those feelings to be supplanted by adoration for the firey pirate.
However, if that original appraisal hadn't been subverted, Ace could raze the high seas. Ace's origin doesn't make the possibility of a heel turn unlikely either. The situation escalates tremendously if Ace had opted to join Blackbeard's crew instead of battling his former crewmate.
2 Monkey D. Luffy
There are various ways that Luffy could descend into evil. If his love of piracy remained unfettered in this alternative reality, Luffy would still have a hefty bounty, but for more violent crimes.
The more interesting route for an evil Luffy would be him aligning with either his father, Monkey D. Dragon, or grandfather, Monkey D. Garp, to initiate his turn to the dark side. As either a revolutionary or marine, Luffy's charisma could summon a host of vile underlings to enact his twisted aims.
1 Usopp
Usopp's upwards trajectory in relevance and competence throughout One Piece is a massive testament to his resourceful cunning. When tested, Usopp not only rises to the occasion, he showcases how deceptively genius he is. If he focused on the pillaging aspect of piracy, Usopp's bluffing and marksmanship could make him the One Piece version of a more menacing Captain Jack Sparrow.
Also, as seen in his fight with Luffy, Usopp has layers of effective machinations and countermeasures at the ready when combating a known opponent.
