One Piece's Sanji is the cook of the Straw Hat Pirates and one of the strongest members of the crew. He joined Luffy on his quest to become the Pirate King at Baratie, back in East Blue, however, Sanji actually hails from the North Blue and has ties to the Vinsmoke Family.
With the Whole Cake Island arc properly explaining Sanji's past to the fans, it also gave him a major power-up for Wano at the same time. Sanji gained the scientific boost of the Raid Suit using which he becomes "Stealth Black." Here are five One Piece characters Stealth Black can defeat and five that he can't.
10 Can: X Drake
X Drake is one of the Worst Generation members and like Sanji, he comes from the North Blue as well. He's one of the Flying Six of the Beasts Pirates and used to be a high ranking member of the Marines, which means Drake is quite powerful.
Drake wields the power of the Allosaurus Ancient Zoan Devil Fruit which grants him great strength and durability. However, Sanji, with the Raid Suit, is more than capable of taking Drake on in battle.
9 Can't: Luffy
Luffy is the captain of the Straw Hat Pirates and also a member of the Worst Generation. Right now, Luffy is one of the most fearsome people to sail the seas of One Piece, and being Sanji's captain, it's no surprise that he's stronger than him.
Luffy has gotten stronger over the course of years and right now, he's mastered two out of the three advanced Haki types. With all those powers, Luffy would not find beating Sanji to be all that troubling.
8 Can: Doflamingo
Donquixote Doflamingo is the former Captain of the Donquixote Pirates and a Shichibukai. He was defeated by Luffy during the Dressrosa arc and later arrested by the Navy for his crimes. Sanji and Doflamingo clashed during the Dressrosa arc and it was quite easy to see that the latter was much stronger at the time.
However, now, Sanji has more than a few tricks up his sleeve, as he displayed in his fight against King of the Beasts Pirates. With power as great as that, beating Doflamingo shouldn't be too hard for Sanji.
7 Can't: Katakuri
Charlotte Katakuri is the strongest of the Three Sweet Commanders of Big Mom and a man worth over a billion berries. He's an incredibly difficult person to take on in a battle, all thanks to his Haki mastery.
Although Sanji's very own Observation Haki is great, it's not quite on the level of Katakuri's. Therefore, Sanji won't be able to land a blow on Katakuri unless he's able to see the future for himself.
6 Can: Capone 'Gang' Bege
Another Worst Generation member, Bege is a powerful pirate who has a bounty of 350 million berries on his head right now. In terms of fighting prowess, Bege is quite decent and his biggest asset is known as Big Father.
While he's very impressive, Bege also lacks mobility and it's quite easy to hit him thanks to his humongous size. With the speed, invisibility, and firepower of the Raid Suit, Sanji should find it feasible to take out Bege.
5 Can't: King
King is one of the three right-hand men of Kaido of the Beasts Pirates and also the strongest of the lot. He's an Ancient Zoan Pteranodon user whose power and speed are both mighty high.
King is extraordinarily tough. Although Sanji can fight King, defeating him appears to be difficult for the Straw Hat pirate at the moment, even with the Raid Suit on. The only way for Sanji to defeat King would be for him to gain further power boosts as the fight proceeds.
4 Can: Killer
The right-hand man of Eustass 'Captain' Kid, Killer is also a Worst Generation member with a bounty of 250 million berries right now. He's quite agile and is great at ripping apart his targets which is partly responsible for him being called the Massacre Soldier.
Killer is, undoubtedly, a worthy foe for Sanji. That said, whatever firepower Killer has at his disposal falls short of everything that Sanji can use against him.
3 Can't: Smoothie
Smoothie is one of the Three Sweet Commanders of the Big Mom Pirates and the second-strongest member with this rank after Katakuri. Although Sanji might be capable of defeating her with the powers of the Raid Suit, he still can't bring himself to hurt her because of his moral code.
Essentially, it is impossible for Sanji to defeat Smoothie no matter how strong or weak she is. Sanji is destined to lose every single battle every time.
2 Can: Cracker
Another member of the Three Sweet Commanders, Cracker is a master swordsman who has a bounty of 860 million berries on his head. Cracker has fought Luffy in the past and managed to overwhelm him even in his Gear Fourth state, showing that the Big Mom pirate is tremendously skilled.
In a fight against Raid Suit Sanji, Cracker would feel defenseless since he would not be able to see his opponent. Cracker is also much slower than Sanji.
1 Can't: Big Mom
Big Mom is one of the Yonko of the Sea and a fearsome pirate considered to be equal to Kaido in terms of power and reputation. Big Mom is a monster in combat who cannot be taken down by the likes of Sanji.
Sanji might not attack Big Mom since she's a woman but even if he did, there is not much he could do to prevent himself from falling to the might of a Yonko.