Just listened to Watershed again. Heir Apparent pretty much kicks ass. Funny, one of the most kick ass Opeth songs on one of their more mellow records.
Right around 5:10 .. when everything comes back in after the slower ambient sounding part and Mike just lets go with that deep low growl until the end of the song..
It never gets old to me..gives me the same feeling I get every time I listen to the opening of Black Sabbath (the song).
then in some other order ..Deliverance and The Grand Conjuration
Although not being entirely heavy and brutal tracks, i believe that deliverance and masters apprentices are their heaviest ones(just listen to those opening and closing riffs)
Loads of their heavy songs have those small acoustic breaks, plus they have quite a few songs with heavy riffs but less heavy vocals. Anyway, I'd still say Wreath, maybe, or ..The Leper Affinity, Karma..eugh, pretty much what everyone else said.
For me I'd have to say the beginning of Deliverance, beginning of April Ethereal and When, the end of Karma (always gets me headbanging in my car), The beggining of Masters Apprentices and Wreath. Like people have been saying.........no overall heaviest song, just really heavy parts. THE heavy riff in Hessian Peel rapes skulls!! theres too many tasty heavy riffs to name!!!
Heir Apparent - stomps u into the ground
Wreath - even the title sounds like "wraaah"
The Grand Conjuration - that riff around 6:30 always somehow reminds me of tearins human flesh...
Blackwater Park and Deliverance or Baying of the Hounds maybe also...