Rance: Sabaku no Guardian

Both shows revolve around comical battles, nudity, light sex with a slave character, and an asshole protagonist. 

Both are 90s fantasy anime about a sex-crazed main character bent on having sex with all women in the show. 

Both are hentai with a fantasy theme and setting, the protagonist in Rance has a lot more of personality and is fun, but both make out with all or most of the female cast. 

Mushoku was inspired by Rance, which makes Rance like Mushoku's cooler older brother. The main character Rance was the main inspiration for Paul, only we're not supposed to think Rance is cool or pine for the days when male characters could be written this way without SJWs trying to "cancel" the series. We're supposed to laugh at him. Rance is intentionally a piece of shit whose frequent rapes, physical abuse of his slave, and awful dialogue are entirely played for dark comedy. Rance is basically Conan the Barbarian portrayed as a 1980s anime pervert. Like Mushoku, Rance is a Western Fantasy and RPG inspired power fantasy for horny young men. However, it never makes the mistake of taking itself seriously or actually asking the viewer to like or respect Rance as a person. Even his name is seemingly taken from the English word "Rancid" meaning "smelling unpleasant as the result of being old and stale". If you wish Mushoku was written a lot more like the original Dragonball or Dr Slump, this is the anime for you!  read more 

Similar protagonists. Similar survival/wasteland themes. Similar "ecchi-ness", though "Rance" is an outright, Hentai production. Both are also hilarious Comedies! The jokes are nonstop.