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VERGO

Vergo was a Marine vice admiral. He possesses immense physical strength and he’s an extremely skilled and powerful hand to hand fighter. He could completely overpower Tashigi, an expert swordswoman, and also the entire Unit 01 of G-5 Marines. He easily fought against Sanji and combined with his Haki, he defeated Smoker in one on one combat.

Vergo is highly proficient in 'Busoshoku Haki'. He is capable of imbuing his entire body with Busoshoku Haki. This form grants him powerful blows that gave both Rosinante and Law a very severe and traumatizing beating. Despite this, he was still unable to keep Law from slicing him in two along his waistline, as Law’s power had improved dramatically since the last time the two had fought.

In my observation this man is a silent type person but very dangerous if picked a fight.
He has the ability to turn a single material into an armament haki and it grants a great durability and to be used to fight for an enemy. This is one of the reason why he was called as very strong.