The shadows as a group start off as emotionless copies of the students, but develop SlasherSmiles very, very quickly until they're actively going out of their way to break their originals and everyone they love.
Shadow!Grenn's prosthetics are just a little bit too creepy.
After he and shadow!Mei slaughter their originals, Gino's shadow drags around his still-warm body specifically so it can find Suzaku and break him with it.
"Hey, Suzaku! Check it out, I finished the job for you~!"