If you're looking for manga similar to King of Hell, you might like these titles. All recommendations are made by Anime-Planet users like you!
Ichigo Kurosaki is an average high school boy with a not-so-average ability to see spirits - something that hadn't affected his life much until a strange woman entered his room one day. Named Kuchiki Rukia, she's a shinigami who was sent from the spirit world to destroy a hollow - a dead-soul-turned-monster; and much to her surprise, Ichigo can see her. When the hollow suddenly attacks his family, Rukia intervenes and is injured in the process, leaving Ichigo to fight it himself. But when Rukia lends him her shinigami powers - which is forbidden - he inadvertently drains them away and has no way to return them. Now, Ichigo is a full-fledged shinigami who must juggle his studies with his newfound duty of fighting hollows; but having gained his powers through forbidden means, the spirit world isn't going to leave Ichigo alone. Ichigo and Rukia must keep their situation a secret from the other shinigami, or the consequences could be dire.
Both series have MC who can see spirits and slay/save them.
While KoH follows exploit Majeh, A legendary swordsmen who is employed by king of hell to slay evil spirits escaped from hell which have huge threat to humans.
Bleach is tale of Kurosaki Ichigo , A shinigami who goes on quest to save his comrades and fellow humans from hollows and other dangers that may appear.
Both have plenty of supernatural stuff and kickass sword fights.
Both series are fantasy stories following exploits of MC, Ah Gou in case of FSJ and Majeh in KoH.
King of Hell follows story of Majeh who is employed by king of hell to set out on journey and exterminate evil spirits throught world who posses considerable threat to humanity.
Feng Shen JI follows story of Ah Gou and how he and his comrades take on the Gods who stole everything from them, With some unexpected allies and some major tragidies they force there way to etch their name in history.
Both series have lots of action, A super badass MC and fantasy world. Though FSJ art is of God Tier.
If you liked one, You'll enjoy other :)