Eustass Kid has the unfortunate distinction of being downplayed by a good number of One Piece fans.
Let it be known that Kid is not a weak character, despite what some readers may believe. Eiichiro Oda makes it very clear that he is a strong fighter, based on how Big Mom acknowledges Kid directly. However, some people like to downplay him for lacking in impressive feats.
Unfortunately, Kid greatly suffers from fan expectations, which negatively impacts his standing. Fairly or unfairly, he isn't quite the fighter that readers want him to be and gets downplayed as a result.
Note: The following article will contain manga spoilers, so anime-only watchers should beware.
Here are some reasons why Eustass Kid is downplayed by the One Piece community
The Twitter poll above asks One Piece fans to pick the character that currently has the best showing against Big Mom. Right now, Law is leading by a wide margin against Kid, and there are several reasons why this is the case.
Kid suffers from comparisons to his counterparts
Whether it's Luffy using Conqueror's Haki or Law using his Awakening, both of these fighters can bypass their opponent's defenses. They even caused Emperors to bleed from the mouth. This would likely induce a visceral reaction from the reader, since internal damage is very serious.
By comparison, most of Kid's attacks deal with blunt force damage, which cause minor scratches and bruises. His attacks are still effective, but they don't have the same impact as Luffy and Law. As a result, Kid doesn't look as threatening.
Kid isn't very creative with his Devil Fruit
One Piece readers have seen what Luffy and Law can do with their respective Devil Fruits. They are very creative in how they use their special abilities. By comparison, Kid isn't as flashy with his techniques.
Kid has eaten the Jiki Jiki no Mi which allows him to create magnetic fields. This is a ridiculously powerful ability in One Piece. Fundamental interaction is one of the basic forces of the universe. If Kid were to realistically apply his abilities to its fullest extent, he would be nearly unstoppable.
Instead, Kid mainly relies on brawling with his large mecha creations. This will likely disappoint readers who expect more, although that is entirely on them. Nonetheless, these readers believe that Kid is too simplistic with his fighting style.
Kid also hasn't shown much proficiency in Haki
This is arguably the biggest reason why so many people downplay Kid. Unlike most top fighters in One Piece, Kid rarely uses Haki to begin with. It should be a basic requirement at this point in the story, and many readers perceive a lack of Haki as a sign of weakness.
Although Kid is stated to use have Conqueror's Haki, he cannot use any advanced techniques. Many readers would fight it hard to believe he could directly compete with Luffy in a fight, let alone the Emperors.
Note: This article reflects the writer's personal views.