Harry Potter: 15 Spells Ranked From Weakest To Strongest
3. The Imperius Curse (Imperio)
The Imperius Curse is one of the three Unforgivable Curses within the Wizarding World; a spell so deadly, cruel and inhumane, that using it will lead to a life sentence in Azkaban.
Though not quite as extravagant as the other Unforgivable Curses on offer, the Imperious Curse's ability to completely control the will of its target - so much so that they will turn on friends or even commit suicide if ordered - makes it one of the more terrifying spells in the franchise, simply because of the lasting emotional and physical damage it can cause.
It's used most prominently in The Goblet of Fire, where Barty Crouch Jr (disguised as Mad-Eye Moody) uses it on a defenceless spider in front of his class. It's a deeply uncomfortable scene, and shows just how dangerously manipulative it can be.