[TOMT] An animation about a man who goes to underworld/hell and becomes the king

I can’t remember if this animation is from a music video or cartoon series. But the one plot is about a man, who dies / thrown to the hell or underworld. And when he gets there he kills the king demon and becomes the new king. His appearance also changes from that of a man to a demonic form.

After that he takes his army and attacks the world of the living, where he encounters a female demon who is doing the same thing. They then proceed to battle out each other.

The animation style isn’t like anime, but I think it’s something like Primal by Genndy Tartakovsky. Everywhere I looked i keep getting anime suggestions, so I hope anyone here can help me with this one. Any help is appreciated!