I'd recommend some 80ss and 90s manga from Kazuo Koiki and Ryoichi Ikegami (you might tell I'm a huge fan of theirs from my username lol), but its extremely niche today. This is because of their stories, which have really over the top stupid, really over the top shocking, and really over the top fan service. The artwork is always beautiful and unique with a realistic approach to characters, and while the plots are full of stupid, shocl-value and fan service, they always have some underlying theme that makes them work and you can see the good points to their stories (the 1990 and 1995 Crying Freeman movies play this up extremely well). The duo worked on-
Crying Freeman(5-7 volumes depending on publisher)
Offered (2 volumes)
Wounded Man (9 volumes)
Lady Snowblood (can be found as an omnibus)
If you wanna check out their stuff, I suggest Crying Freeman and Lady Snowblood, their most famous works. Also Strain, which has Ikegami's art with a down to earth plot. I'd skip Wounded Man and Offered unless you're a die hard fan of theirs. Offered can be found cheap but is so ridiculous and dumb, plus I needed shock value and fan service, as is Wounded Man which is expensive as hell and full of some dreadful actions of the main character throughout the story, which is a shame because it's a really strong story hurt by stupid and downright over-offensive bits. If you love niche like I do though, the Ikegami Koiki teamup mangas are for you.