Saddest Opeth songs?

Hope Leaves, Isolation Years, When, (the beginning of) Dirge For November, Weakness, To Bid You Farewell, Wreath (the part starting at 1:47 has always sounded especially tragic to me), Face of Melinda, and a bunch of moments from MAYH.
 
Try listening to "Hope Leaves" or "To Bid You Farewell" when someone important to you goes away. When I listen to those songs they bring up memories, good and bad. "Isolation Years" and "Hours of Wealth" are especially good if you are feeling lonely one day too. The acoustic part in "The Amen Corner" is also kind of depressing, at least for me. Everytime I listen to that part it reminds me of my Krystle, and then I get all down. "Dirge For November" is also a really sad one for me.
 
I'd say

1. Dirge for November
2. Isolation Years
3. Godhead's (more nostalgic than sad maybe)
 
the night and the silent water.. thats a genious and very sad song.
I've heard that mike dedicated the lyrics to his grandfather who got away.. really sad lyrics though. and the acoustic parts are so beautiful it makes you wanna cry.

another one to mention would be "hope leaves" also sad in a beautiful way.
 
Lots of sections on MAYH. But Still Day Beneath the Sun is also one of my favourite sulking songs.
 
and so you left us...jaded and gaunt...wilted with seasons...hidden inside the delusion...devoid of death...in solid tears I linger...

I listened to that after my grandfather's suicide. The saddest song ever written.