Harry Potter: 15 Spells Ranked From Weakest To Strongest

What else could possible be regarded as the franchise's deadliest spell that the horrifically titled Killing Curse? Avada Kedavra is a spell so strong that it leaves its targets dead as soon as it strikes them.

The curse cannot be stopped, deflected or survived (unless you're Harry Potter and you're mother's willing to be a human shield).

Over the series, the Killing Curse has taken the lives of James and Lily Potter, Sirius Black, Hedwig the Owl, Cedric Diggory and even Albus Dumbledore, the most powerful wizard of them all.

There's a brief upside in that the death itself is said to be so sudden that the deceased feels no pain, but given the fact that it kills instantly, this isn't too much of a comfort.

Of all the spells in the Harry Potter universe, the Killing Curse is easily the strongest, and certainly the most unforgivable of the Unforgivable Curses.