I don't see how Bloodbath have a place in this discussion. Awesome, yes, but not all that heavy. Although the guitars on Resurrection Through Carnage were pretty heavy. I guess they have a couple moments of truly crushing heaviness, mostly on Nightmares Made Flesh.
The heaviest album that I actually own would probably be In Their Darkened Shrines by Nile.
Heaviest that I've heard is probably Devourment. I should probably check out Wormed, I guess.
Some goregrind can be pretty heavy, too.
It depends on how you define heavy. If you mean how deep and bassy is the sound, then maybe I should mention Incantation. If you mean how fucking brutal and crushing, then I don't really see why doom metal is coming up.