I suppose by perfect I would assume that a band never backtracked or lost a step in their development. Given that criteria, I would go with Gorguts.
Now I know that many will mark Obscura as the high point for this band, and maybe for the death metal genre. As far as technicality is concerned, I think I would agree. Yet for me, I think From Wisdom to Hate was as far as they were going to go structurally. It was able to bring in the quirky, jazzy techniques and death metal riffage of that previous album, and rein it in with Classical structuring.
I can't think of another band that left on such a level.