Such a tough question because I want to shout out songs across multiple subgenres. Death Grips - No Love, Primus - Frizzle Fry (especially the ending), Quo Vadis - Silence Calls the Storms, Rage Against the Machine - Settle for Nothing, Soundgarden - Jesus Christ Pose, Denzel Curry - Ultra (feat Yung Kane , Nell , Slikk , Rell), Vivaldi's Summer 3rd Movement and half of the Acid Bath or Ulcerate catalog. If I have to settle for one song though I think I would go for :
Ahab - Old Thunder
However, if I can choose a particular snipet of a song that I think is the heaviest thing I have ever heard period, I would go for Akercocke - Leviathan, between the marks of 3:30 and 4:00. I was legit scared first time I heard that. You gotta listen to it from the beggining though because that build up is insane.
Glad you liked it ! I think this band is a little bit of a hidden gem. Their albums "The Goat of Mendes", "Words That Go Unspoken, Deeds That Go Undone" and "Antichrist" are really worth checking out.