i too vote for unfaithful. one of my closest friends lost her husband to cancer a few years before my husband went off the deep end. We often talk about our similar feelings of loss, but the glaring difference is that she maintained at first that at least i had the hope of seeing exh and that as long as he was alive he could perhaps turn it around and be the person he was for most of our marriage.
now, well, she gets it: the pain of having someone who looks and sounds like your beloved spouse but behaves like an entirely different person wandering around, having to deal with that person because of kids, etc. Both death and divorce hurt immensely, but divorce ... eh, there's so much more that goes along with that: betrayal, disillusionment as Zues said, etc.
M 20+ T25+ S ~15.5 (BD) BD 4/6/15 D 12/23/16
"Someone I loved once gave me A box full of darkness. It took me years to understand, That this too, was a gift." ~ Mary Oliver