Queen the Plague is an All-Star of the Beasts Pirates and one of Kaido’s three right-hand men, the Disasters. So how are we gonna speculate his devil fruit ability? Through his character design…just like Kaido.
Remember the first time Kaido’s full appearance were shown, people immediately speculated that he has a dragon ability because of his scale tattoo. And even Jack’s human form character design, there’s a clue that he has a mammoth devil fruit and that is the pair of tusk that he carries around his neck (although he was shown in his mammoth form first before his full human form).
That’s why I believe Oda also left a hint on what could be the Queen’s df ability with his character design which were shown in the chapter 925.
So looking at Queen’s appearance, I think there are 3 possible hint about his devil fruit.
1) The markings in his face. We can see that he has a tattoo that forms an X shape and 2 curve lines from his lips to his neck.
2) The Beasts Pirates jolly roger tattoo on his right arm. If you noticed his jolly roger tattoo is a little different because the other end of the middle crossbone is an arrow that crosses to his name QUEEN.
3) His striped clothes.
So using all these hints, I tried to find what could be his Zoan Devil Fruit and I concluded that Queen has a wasp insect zoan. If you look closely in the wasp’s face, you can see that part of it forms similar marking like that of Queen. (Damnnn….. I can’t explain it better as I have no idea what you call those parts of an insect so I’ll just show a pic XD)
Wasp’s body also have stripe pattern…
And the wasp’s stinger could be what the arrow in Queen’s tattoo in his right arm represents.
Having a wasp insect zoan also fits his epithet “The Plague” because wasp is one of the worst insect invaders.
Also, Queen is probably an Okama right? So by having a wasp zoan, he will have an ability that injects something to a person just like another legendary Okama, Emporio Ivankov. Wasp have stinger that inject poison while Ivankov has devil fruit that allows him to inject his specially manipulated hormones to other person.
*Theory by jinz