How does harry potter kill voldemort?

Harry, Hermione, and Ron all end up destroying the Horcruxes, Harry sacrifices himself as the last Horcrux and he's able to survive the Killing Spell yet again. Finally when Voldemort and Harry duel, Voldemort casts Avada Kedavra as Harry casts Expelliarmus, The two spells meet and Harry's is stronger, Avada Kedavra gets sent back towards Voldemort and kills him.