Axel is more or less the Scar to the Devil's Mufasa. Wanting to take over when Satan leaves, he had killed Damien (as in the omen). He is an adverary to the Mushrrom Kingdom because he has tried all sorts of thing to the protaganists. Like selling people off a mail order spouses.
Axel is the son of Satan's brother Archibald. Specifically, Archibald had bred with a fallen angel.
The angel had been pure in her heavenly life. But she soon became promiscuous when she was thrown out and got turned into a demon.
Naturally, having turned promiscuous as a result of Hell’s influence, the fallen female angel had, had… an affair with Satan’s brother Archibald. This led to the birth, naturally, of Axel.Axel is based upon Meowrice from Gay Purr-ee. And his his design is based of that of Lickboot from the Tom and Jerry movie.
But if he wasn't dead, I would cast Paul Frees.
NOTE: I may redo image in future