The Planeswalker in Marvel

With his parents' inheritance to rely on, the protagonist begins studying magic. An accidental mishap gives him the ability to travel to other movies and TV series.

In The Sorcerer's Apprentice, he learns real magic. With a time-stopping spell, he leaves the Abomination standing around in a daze, questioning his life.

In Harry's world, he subdues the Dementors and makes them his servants, sending them into battle during the Battle of New York...

In Percy Jackson's world, he obtains a formula for evolving into a god...

Before he knows it, he completes the mission to collect the Infinity Stones and opens the door back home.