In One Piece, a villain is usually nothing and need a strong crew to support them. Although these crews are often less recognized than their captain, it is still an important part of the overall design of a villain and their empire.
A strong villain in One Piece needs unique characters
To become a strong villain in One Piece, first and foremost, the person needs to have a diverse exciting crew. Each person needs a unique personality and ability to help them differ from all other characters in the ice. In addition, these characters must have a good relationship with their teammates, building a unity, developing together. Above all, the characters must also be quite strong and can resist themselves even the most difficult opponents.
Most importantly, the crew needs close relationships with their captain. This does not mean that their heads and crews need to be close friends who protect each other in any situation. A villain who hates his crew can still have an interesting relationship with them if it is accurately described.
Big Mom and Doflamingo have a great army in One Piece

Admittedly, Big Mom's crew is one of the most interesting and diverse characters, deserving to be mentioned when talking about great villain astronauts. With a diverse “personnel” including the children of Big Mom, everyone has very interesting strength and personality. They all have their own motivation and depth.
Among the favorite characters such as Katakuri and Brûlée, or the hated characters, such as Perospero and Flampe, Big Mom tape is one of the most active villain astronauts.

Next, Donquixote pirates also deserve to be mentioned. Although this tape has a number of characters that are easily hated, the respect that the members have for each other is something that few other villains in the series have. With interesting personalities and characters in every corner of Donquixote pirates, from their favorite to obnoxious, this group becomes one of the most interesting villains that the Straw Hats face.
Cross Guild is the most interesting pirate group in One Piece

However, the best villain gang in the series must mention Buggy and Cross Guild. First, Buggy, as the accidental leader of Cross Guild, created an interesting relationship between him and his own “subordinates”, Mihawk and Crocodile.
Cross Guild has combined many great characters that fans love and respect throughout the series, including characters from the previous gang of Crocodile and Buggy. The fact that Mihawk and Crocodile are in this gang is enough for Cross Guild to become the best villain gang. With iconic characters like Daz Bones, Galdino and Alvida are also in their ranks, this gang has some incredible potentials in the series.
While these three groups are extremely strong villains in One Piece, in the end, the best villain group depends on personal preferences. Some aspects of the crew of each villain are more liked by some fans than other aspects. Finally, most important villain groups in One Piece are built extremely well.