Melissa's final moments before she's taken over completely by Eve. Her diary was sad enough, with her desperately trying to be ready and in shape to play the role she's been wanting for ages, worrying about her sickness getting worse and the extensive medication she needs to take. Then after Eve makes her debut and torches the theater, Melissa still has some of her faculties and runs off to a rehearsal room and plays the piano. When you see her, she's playing the Main Theme, a slow and sad piece in itself, while talking to herself that she's still her, desperately trying to maintain her identity, before Eve takes over completely and Melissa is gone forever.
The moment where Sheeva transforms into a monster while Baker and Ben can only watch in horror can hit too close to home for anyone who's had to put down a dog; Baker even tells Ben to look away before shooting at the mutated Sheeva, but runs out of bullets before Sheeva retaliates. By the time Aya arrives, Ben, realizing Sheeva is gone, pleads for her to kill it! Eventually, Aya does, and it's very sad knowing Sheeva was such a nice dog who befriended Ben but, knowing she was turning, tried to run away from Ben so she doesn't hurt him. If you're a dog lover, then you'll cry during this boss battle.