By adult I mean over 18-20 years of age and with adult appearances. Nothing against anime with younger characters, but interested in finding some with older characters.
What you want is “seinen” anime, which is intended for an older audience. Most anime is “shonen”, which is intended for kids. (Not that there’s anything wrong with an adult enjoying shonen.) There are more genres and specifications, but I am not that into anime.
Dragonball is shonen. Cowboy Bebop is seinen. There are loads of great seinen shows out there.