Dr. Hogbackドクトル･ホグバック

Dr. Hogback is a skilled surgeon who entered the employment of Gekko Moriah, assisting him in creating his undead army. He is one of the major antagonists of the Thriller Bark arc, and one of the Mysterious Four.

Hogback is immensely arrogant and is extremely proud of his reputation as a genius. However, despite curing numerous people with his abilities, Hogback considers his patients a necessary nuisance in order to acquire greater wealth and power.

Hogback also believes that through the use of Moriah's power he has finally managed to overcome death, restoring corpses to life as his zombified slaves. Hogback dismisses the fact that the personality of the zombie is vastly different from the way they acted in life. He cares little for the fate of his undead creations or the people whose shadows were stolen to create them.

Source: Wikipedia