Even Outbreak, a side title, manages to be depressing. 8 people fighting desperately to survive, seeing familiar friends, co-workers, and family all shambling undead. Cindy sees her co-worker eaten alive, Jim may be forced to kill some of his own co workers, Kevin witnessing the fall of the RPD...Even Bob, Mark's friend, can get this troper misty eyed. The only one who seems not to go through any variety of trauma at all from the incident is antisocial plumber David.
YMMV on David not suffering either. Through the entire game he seemed enraged at the entire situation and most determined to survive. Then consider that his fighting could all have been in vain... "I'm supposed to feel awful, but I felt like laughing. Why? Well it really doesn't matter now...does it?"
This troper could barely watch the intro to "Wild Things" when he figured out what he was seeing. I'm a big animal lover. Seeing that, I had to put the controller down for a while before I could continue.