What's the heaviest DM you've heard? It doesn't have to be brutal like suffocation, because iron maiden is as heavy as some death metal bands just cause the riffs are so metal. For the heaviest...I'd say Peace Sells, None So Vile, and Black Metal (Of the entire Metal genre)
For death metal...
None So Vile
Covenant
Legion
For death metal...
None So Vile
Covenant
Legion