More sludge than doom but the two genres are kissing cousins. Might I suggest Reverend Bizarre? They're the best thing since sliced bread as far as I'm concerned.

Show me the metalcore that's early proto **** (f.ex. Groundwork, Ringworm, Starkweather, Rorschach, All Out War). Gotta be raw and doesn't have to be metal metal.

Show me obscure thrash that's amazing from any time period, though 90s is appreciated. Blue Hawk need not apply unless he can develop some taste.

Coroner - Mental Vortex

Not nearly obscure enough.

I've heard Pestillence's first album is pretty good, and I remember reading awhile ago that Xentrix's second album was decent.

Recommend me some Death Metal like this
 

Heavy, not too fast, angry, brutal

https://www.youtube.com/watch?v=Rn1GNxNToUM

https://www.youtube.com/watch?v=4q5ylaZahFU

https://www.youtube.com/watch?v=rzQ1O57ocp0

https://www.youtube.com/watch?v=mHJPkOejtOg

https://www.youtube.com/watch?v=m0AhnOwubnA

This is some nice heaviness that ain't too fast. How much are you into death/doom btw?

Crawlspace is good, Coffins not so much - too bland.

I'm into it quite a lot. Mostly death and black metal. But I have very specific tastes and not much time to listen to music, so I don't know that many bands or songs.

I meant death doom metal. Death metal with a doom metal influence, or doom metal with a death metal influence. For someone looking for death metal that's not going a mile a minute it's not a bad way to go.