In a series like One Piece, it isn't hard to find great fight scenes. However, with more than 1000+ episodes, it is easy for some great fights to slip through the cracks and become somewhat forgotten over time. This is especially unfortunate, as even the obscure fights of the series tend to be some of its highest points, which is par for the course when talking about the "Big Three."
A consequence of this is that it becomes easy to lose track of the fights in the series that don't actually feature any of the Straw Hats. The perfect example of this might be the fight on Punk Hazard between Trafalgar Law and Vice-Admiral Smoker against Vice-Admiral Vergo. As this fight featured only two side characters and a villain that wasn't seen after the arc concluded, it's easy to see why this fight hasn't gotten the love it most certainly deserves.
Taking place during the Punk Hazard arc on the titular island, it makes sense why this fight isn't often brought up. This specific arc was in many ways nothing more than a setup for the much more important and much longer Dressrosa arc that came right after. Which in itself was meant to be a prelude to the current and also very long Wano arc, and featured most of the same characters to boot. This happened to make Punk Hazard feel largely forgettable in the grand scheme of things.
Regardless of everything though, Punk Hazard definitely had one of the series' best fights. Featuring two fan-favorite characters, Smoker and Law, having to team up to take on the incredibly strong Vergo was a true treat to behold. While the arc's primary antagonist was meant to be Caesar Clown, Vice Admiral Vergo became just as important and arguably much more dangerous. He had no Devil Fruit powers, but he did have a mastery over the relatively newly introduced Haki, making him a perfect villain for post-time skip One Piece.
With the power and importance of Haki being brought up by many characters, specifically Rayleigh during Luffy's training, it was a little strange it took so long to really see what a master of it could really do. It was also surprising to see that character be a villain, which further added to the hype surrounding the power. In Vergo's first fight on the island against Sanji, he showed that his Armament Haki was stronger than Sanji's; enough so that the Straw Hat's cook was worried that repeated attacks would cause the bones in his legs to break!
As cool of a villain as Vergo was, the true reason this fight is so fantastic is that it showcased just how far Smoker and Law had come since pre-time skip. Neither character had been seen since the Marineford arc, and even then their roles were largely minimal. Viewers had some idea of Law's abilities based on scenes and moments prior, but they'd never really seen them or the character pushed to their respective limits until this fight.
Smoker's growth was also very fun and interesting to see, maybe even more so than Law's. Having been the first Logia user introduced as well as being the first villain Luffy had to escape from, Smoker had always been portrayed as a strong character. Unfortunately, as the series progressed, more characters were introduced and many of them seemed even stronger than Smoker. It didn't help that his Logia's element wasn't inherently the strongest either, which led to his perceived strength being further undermined. Thankfully this fight showed just how dangerous and powerful the Vice-Admiral had become, especially when he combined his Devil Fruit power with his newly acquired Haki abilities.
The ensuing fight between the three was an incredible spectacle to watch and read. With Law using his control over space to attempt to trick their foe and Smoker using his abilities to try and overwhelm Vergo, it was hard to believe that neither was capable of beating the traitorous marine until they started working together. In fact, it was only when the two began trusting one another that they actually managed to gain the upper hand and secure the win. By tricking Vergo with a barrage of attacks, Smoker returned Law's stolen heart to him, which in turn gave Law a chance to finally cut down their mutual foe as well as the factory he was protecting in one strike. The scene itself is immortalized as one of the series' most epic.
The fight also led to many great character moments for both Law and Smoker. In Law's case, it showed that his Haki (a manifestation of the user's will) was greater than Vergo's. This highlighted just how much his crusade against Doflamingo meant to him. For Smoker, a character who has always had a strange relationship with pirates since his introduction, it gave him more reason to respect them. He's a character that believes in the Navy's duty as well as their position but isn't so jaded by his post that he loses sight of who the real bad guys are, which has always made him a likable character. This fight further developed that.
Looking back on the series as a whole, it's easy to see why this fight gets overlooked. It has none of the Straw Hats and features a one-off villain. Regardless of that though, it still manages to be incredibly exciting and further develop the characters in the way that all the best One Piece fights have. It's arguably the best fight either of these characters has had in the series so far and should definitely be remembered as one of One Piece's best.