I don't read a whole lot of fighting genre, but Girls of the Wild's is good. But it's a Korean webtoon, so I don't know how you feel about that... Not the conventional manga, but it's a good kind of different. Highly recommend XD
You can also try Hakaiou Noritaka!. It's a manga about kickboxing - haven't tried it myself, but from a couple of glimpses it's REALLY funny.
Okay then, fighting manga with flawed heroes and grey morality.
Übel Blatt - one of my favourite antiheroes. He's also got a badass sword A Fairytale for the Demon Lord - perhaps, I've only read six chapters yet Ajin - it's basically about zombies. Has the grey morality thing down. There's also some fighting (for one's life) Aletheia - that mc... I can't tell you why he's interesting without spoiling you a bit, but since it's still got just a few chapters out, it's pretty quick to read. The story''s moving kind of slowly though Be Heun - a retired badass war hero, if I remember correctly. not 100% sure if this is what you seek Black Haze - okay, this is just Good (attention to the italics and capital letter) even though it's not exactly what you've asked, it's got some fighting and the mc is no saint. he's also very pragmatic Chang Ge Xing - sorry I keep giving you strategy recs, but this is just so surprisingly good Godly Bells - mc seems kind of wimpy at first but turns out to be very interesting Gun x Clover high-ranked in disguise. has dark past, wants revenge, etc etc In Full Bloom (YON Jae-Won) One ruler, one schemer, and... one assassin. Need. I. Say. More!? Itsuwaribito Utsuho he's a liar with heart of gold. Also pretty crafty Jormungand and probably Black Lagoon but I prefer Jonah to Rock Waltz The mc's an assassin and pretty flawed Vinland Saga Goddammit read it NOW it's got BLOOD, it's got REVENGE, it's got a FLAWED MC, it's got EVERYTHING Yongbyeong Maluhan probably Ares set during wartime if I'm not wrong, so lots of grey morality
maybe (probably) not all of them are what you're looking for, but most of them are really good
edit: also seconding 1/2 prince, eclipse hunter, sun knight and girls of the wild's also has a lot of fighting
The Legend of Sun Knight (Novel) is one of the best novels ever written but it doesn't have that much action. The lead's personality is amazing! He is devil who is a saint!!
Noblesse Cool fights. Protagonist is smart, cool & silent. Not your usual shonen... The starting is slow so bear with it till Ch.70 or so.. Akame ga Kiru! Feng Shen Ji It's popular in action/fantasy genre. Not a fan of it but it has large fanbase. Berserk