Zhong Kui, the King of Ghosts!

Chinese Deity

Extremely intelligent

Died by running into a door repeatedly when the emperor rejected his genius due to Zhong's appearance.

Ruler of the underworld recognized Zhong Kui's genius and employed him to hunt demons.

Has a demon bag where the spirits are kept. Can hold any amount before they need to be returned to the underworld. Uses talismans to combat evil, for restraining and capturing demons. Has demon-killing sword and is very skilled with it.

Grey skin, huge but muscular belly, tiny legs, long arms, insane beard that defies gravity and spikes out sideways. Very strong. Basically all muscle.

Zhong Kui is a Taoist deity in Chinese mythology, traditionally regarded as a vanquisher of ghosts and evil beings. He is depicted as a large man with a big black beard, bulging eyes, and a wrathful expression. Zhong Kui is able to command 80,000 demons to do his bidding and is often associated with the five bats of fortune.

According to folklore, Zhong Kui travelled with Du Ping, a friend from his hometown, to take part in the state-wide imperial examinations held in the capital city Chang'an. Though Zhong Kui attained great academic success through his achievement of top honors in the major exams, his rightful title of "Zhuangyuan" (top-scorer) was stripped from him by the then emperor because of his disfigured and ugly appearance.
Extremely enraged, Zhong Kui died by continually hurling himself against the palace gates until his head was broken, whereupon Du Ping had him buried and laid to rest. During the divine judgment after his death, Yanluo Wang (the Chinese Underworld Judge) saw much potential in Zhong Kui, intelligent and smart enough to score top honors in the imperial examinations but condemned to Youdu because of the strong grievance. Yama then gave him a title as the king of ghosts and tasked him to hunt, capture, take charge of and maintain discipline and order among all ghosts.
After Zhong Kui became the king of ghosts in Hell, Zhong Kui returned to his hometown on Chinese New Year's eve. To repay Du Ping's kindness, Zhong Kui gave his younger sister in marriage to Du Ping.