Helck

Both involve a hero that has changed affiliation to the demon side to wage war against Humanity. The demon lord opposes the hero in both categories. But eventually sees them as an aid to the demon army 

- Both MCs are strong with their physical prowess and both kinda silly on their own. - Both are somewhat an outsider in their respective story with Mash as a non magic in magic school and Helk as a Human in demon world. - Both MCs somewhat despised by some high-ranking Wizard in Mashle and Demon in Helck. - Both has supportive sidekicks. 

Both are about an incredibly strong man joining an army of demons, And both are about creating peace between humans and demons, 

Both are action series with a heavy bent on comedy featuring an impossibly strong human hero who takes down all kinds of demons without much effort. Obviously don't expect the level of visuals OPM has in Helck, but they're pretty similar in tone and theme. 

Red Head Tsundere suspects the super powerful protagonist is evil and stalks him and tries to get him to reveal his intentions. Both shows feature a demon leader/human leader combo that are forced to work together. There is a lot of comedy because of the situation in both.