Off the top of my head, Darker than Black. Same director, different take on bleakness: Wolf’s Rain. The main characters don’t really have ‘ages’ given, but they’re pretty clearly adults.
Record of the Lodoss War (a D&D campaign turned into anime, if I recall rightly)
That time I reincarnated as a slime (technically the main character is ~34, and very few children are shown, but the cast has a lot of ‘childishness’ in them… the style is the equivalent of a popcorn superhero movie I’d say)
Legend of the galactic heroes
Witch Hunter Robin
Van Helsing (if you just want to laugh at idiocy, simply watch the abridged series, but the actual show is good)
Dragon Ball Z, except for a few episodes every now and then. The show itself is obviously aimed at the younger shonen crowd though, if you haven’t seen it.
.hack//sign (dot hack sign) is a pretty interesting one. It has several other series in its ‘canon’ if you like it. I’d say it was the adult oriented, well-presented premise of sword art online before sword art online was wet-dreamed up. A friend described it as ‘waving its dick around because they had an actual orchestra for the soundtrack’ in several scenes.
Well, I guess I am now doomed. All these women chasing me will know exactly how to catch me. Oh no, oh woe.