Get ready for the feels.
Tom Riddle/Lord Voldemort
Death: Harry Potter and the Deathly Hallows, killed by Harry Potter.
Voldemort was just the actual worst. He killed people for no reason — including his own supporters — and all he cared about was power. Everyone cheered when he died, and for good reason.
Warner Bros.
Bellatrix Lestrange
Death: Harry Potter and the Deathly Hallows, killed by Molly Weasley.
There was nothing good about Bellatrix other than her apparent love for Voldemort. She put him over her family, and eventually died fighting for him. So she sucks.
Warner Bros.
Nagini
Death: Harry Potter and the Deathly Hallows, killed by Neville Longbottom.
Nagini was just an animal, so we can't really blame her for biting people's necks - but she also contained a part of Voldemort's soul. So she sucks. (Pun intended.)
Warner Bros.
Professor Quirrell
Death: Harry Potter and the Philosopher's Stone, killed by Harry Potter.
Not only did Quirrell try to kill Harry when he was only 11 years old, he also killed several unicorns and set a troll loose in the Hogwarts dungeon on Halloween. Oh, plus the fact that he had Voldemort sticking out the back of his head.
Warner Bros.
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The Definitive Ranking Of "Harry Potter" Deaths By Sadness