Expelliarmus

Introduced in Harry Potter and the Chamber of Secrets as a basic Disarming Charm that produces a dazzling scarlet flash and blasts opponents off their feet while expelling their wands, Expelliarmus quickly evolves into Harry's signature spell across the series. From a defensive tool in duels against Draco Malfoy, it becomes a pivotal weapon in battles against Death Eaters and even Voldemort himself, symbolizing Harry's commitment to non-lethal magic. By the later books, its mastery underscores Harry's growth from novice wizard to the hero who defeats the Dark Lord with a disarming spell in the Battle of Hogwarts.