Slayers album, Reign in Blood is considerd by most if not all to be the best thrashmetal album of all time.
I dont think one song on there is over 6 minutes long 
Yeah, by those who knows NOTHING about heavy metal. There are only 2 good songs on that album, "Angel of Death" and "Reign in Blood", the rest is bullshit. I don't even like thrash all that much, but I know there are much better by the likes of pre-1990 Metallica, Megadeth, Incubus, Overkill, Kreator, Sodom, etc.
I'm an expert on Godly doom metal, not trashy thrash crap.
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Pentagram is a much better band than Slayer ever were.