Pat's murder and Sara's death. It's widely considered one of Argento's masterpieces and most gory movies.
The death of the blind pianist. Imagine your dog attacking your throat without any apparent reason whatsoever. Combined with Nausea Fuel when the dog begins ripping out strands of flesh and sinew.
The maggots in the ceiling and in every student's hair and/or face may be this for some people.
'I'm coming, American! And let the living meet the dead, and the dead the living...'
"You want to kill me? You want to kill Helena Markos?!! *Evil Laugh* Now, death is coming for you! Hell is behind that door! You're going to meet the dead now! The Living Dead!!! *the door slams open, revealing...*
Sara's reanimated corpse makes the final confrontation all the more disturbing.
One could argue that the pins in her freakin' eyes that probably contribute to her body's twisted reanimation make it even worse.
The inhuman snarling before the door opens, and the way Sarah's corpse just fades away after Suzy kills Helen
When Suzy flees after killing Helena, she catches a glimpse of the rest of the coven, basically almost every other adult living at the school, writhing in agony as they die without their mistress to sustain them. Suzy escapes the school just in time to see the entire building go up in flames
The Creepy Child who's implied to be the grandson of the headmistress of the school. Albert's also a clear inspiration to Scissorman from Clock Tower, right down to the old-fashioned boys school uniform.
