Master of Puppets always struck me, especially upon some retrospect of it that I underwent a couple years ago, as the product of a cohesive unit just totally and utterly within its stride. This results in a somehwat clinical proceeding, but is nonetheless precise and deadly all the same. They knew exactly what they were doing and how they were going to do it. It's almost thrash by numbers, yet I mean that entirely non-pejoratively. It's not my favorite Metallica album (I go back and forth between the first two, for very different reasons), but to call it "bad" is just ludicrous and most likely the result of a pretty superfluous understanding of the album.
Also, Slayer, especially up through Reign in Blood, is so obviously the best thrash metal band ever that it's amusing to even debate the fact. Oh, and by the way, Velocibrad, I do know a fair amount of thrash metal bands. I know, it's weird. Yet Hell Awaits is superior to [abandoning italics here to avoid monotony] Bonded by Blood, Darkness Descends, Swallowed in Black, Last Warrior/Ostatni Whateverthefuck, The Force, History of a Time to Come, Campo de Exterminio, Abominable Anno Domini, Spectrum of Death (Slayer with Iron Maiden's mascot), Doomsday for the Deceiver, Terror Squad, Infernal Overkill, Persecution Mania, Pleasure to Kill, Golem, Fragments of Insanity, A Tribute to Insanity, Finished with the Dogs, Taking Over, Killing Is My Business...and Business Is Good!, Forward to Termination, Strappado, Evil Invaders, War and Pain, Kill for Pleasure, Power and Pain, None Shall Defy, Bloody Vengeance, The Unholy One, Possessed by Fire, Merciless Slaughter, Tales of Terror, Hymn to Abramelin, Into the Abyss, Behind the Realms of Madness, Above the Ashes, Metal Deadness, Breaking the Silence, Mind Wars, Energetic Disassembly, Satan's Gift, Recognize No Authority, Mayhemic Destruction, R.I.P., Vengeance of Hell, Mekong Delta, Immortal Force, Heresy, Serpent Temptation, Recipients of Death, The Kindred, Total Armageddon, Schizophrenia, World Circus, Suffering Hour, Final Genocide, Hobbs' Angel of Death, Rather Death than False of Faith, etc.