As the title suggests, I'm looking for a Manga that is dark, serious and gritty, something along the lines of Berserk, Monster, vinland saga

I dont mind the story, whether it be magic, action, crime, ancient times. As long as the story and plot is good, I'm down for it. 😎

Might as well put some famous ones out there, but you've probably read a lot of these already given your current examples:
Freesia
Mugen no Juunin
Vagabond
Gantz
Hellsing
All You Need Is Kill
Battle Royale
Maybe:
Historie
Terra Formars
Uzumaki no big "heroes" here though
Aku no Hana & Swweeet rely on psyche and angst rather than edge and grit
Soil @calstine's right; it's surreal, to say the least
Skyhigh

Jiraishin, definitely; the Skyhigh saga, maybe. Check out the mangaka's other series, too; especially Blue Heaven and Sidooh.

Innocents Shounen Juujigun
Akira
Kozure Ookami
Shuto Heru

Sanctuary, Heat, and other titles by the same mangaka.

I second Freesia. On that note, a lot of Matsumoto Jiro works would fit your request pretty nicely.

Another author you might want to try is Kitoh Mohiro.

Eden - It's an Endless World! and other stuff by Endo Hiroki.

Soil is a good one, but it has quite the insane edge to it, so if you're looking for very realistic stories you may not enjoy it.

Possibly Homunculus, but, like Soil, it's bizarre -- though in a completely different way. It's also more on the introspective side, so there's no action at all.

Kiba no Tabishounin - The Arms Peddler
Dorohedoro
Rainbow (I'm not sure about this one, I stopped reading it early, it was too much for me)
Priest

Battle Angel Alita and Battle Angel Alita: Last Order
Haven't started reading Battle Angel Alita: Mars Chronicle yet tho
Zetman as well

Edit: Until Death Do Us Part too

Kimi no Knife can get really dark. The main character is a hitman and its great.

Homunculus is just a mindfuck of a manga and super psychological. Its not so much dark as it is psychologically dark.

Both are pretty much my absolute favorites that I couldn't put down.

Why am I like this

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