It’s been years in the making. The entire Marvel Cinematic Universe has been leading up to the Avengers facing their biggest challenge yet - Thanos.

With the 4th Avengers movie dropping the title of "Infinity War part 2," many are left wondering what that change was all about. The official explanation from Marvel is that they are keeping the film’s title a secret for now, as it would spoil the ending of "Infinity War." Fans have gone berserk with their theories about how "Infinity War" could end.

Here are our Top 5 picks:

Infinity gauntlet

It’s a no-brainer that "Infinity War" is all about Thanos pursuing after the Infinity stones.

In the original comics, Thanos was just a hopeless romantic who snapped his fingers with an Infinity gauntlet armed with all the 6 Infinity stones to wipe out half the life in the universe- to impress his lady, death herself. Even though Kate Blanchett already introduced ‘Hela, the goddess of death’ in "Thor-Ragnarok," fans think that Thanos won’t have any interest in her in the upcoming movies.

As the trailer says, his mission seems more to ‘rebalance the universe as he sees it’ and the "Infinity War" is just that. Both Kevin Feige and the Russo brothers have said that "Infinity War" will be a heist movie, with Thanos scheming and acquiring the Infinity stones, one by one. So the number one theory on how the movie could end is with Thanos having stolen all the 6 Infinity stones and throwing out his infamous smile at the audience.

Death of Iron Man

Robert Downey jr rose to the spot of being the highest paid actor in Hollywood following his 2008 depiction of "Iron Man." And it was not just Robert who climbed up the ranks; he took the entire Marvel Cinematic Universe with him. While many credit the entirety of MCU’s humongous success to Robert alone, he is without a doubt the fan favorite of them all.

So what better way to close off "Infinity War" by sacrificing Iron Man, the one who started it all?

The theory that started out as a rumor has gained traction with RDJ’s statements of a possible retirement from the MCU. The trailer clearly shows a distraught and defeated Tony Stark, not Iron Man. Could this mean it’s time to prepare ourselves for a world where RDJ isn’t Iron Man?

Avengers destroyed

Yes, you read that right. Marvel is ending their phase 3 with the 4th Avengers movie. So it confirms that we will have to bid goodbye to some of our favorite characters, especially as many of them reach the end of their contract with the conclusion of phase 3. Now for a film franchise as beloved and successful as Marvel, this won’t be an easy transition.

They need to take the stakes to never-before heights to sacrifice the fan favorite heroes, and who better to avail that than Thanos! In the comics, Thanos basically kills almost every hero with just a snap of his fingers, and the end of "Infinity War" could very well be that, with Thanos standing atop a pile of dead Avengers.

I know what you are saying, then how could the Avengers come back to life to defeat Thanos in the 4th movie? Doctor Strange, isn't it obvious?

Soul stone reveal

One of the greatest movie mysteries of this millennium, the soul stone! The MCU has been playing the ‘stone cards’ very close to their chest, as they are basically their most valuable assets considering the path leading to "Infinity War." Introducing the stones one by one in important movies and with carefully placed conceals that gives a ‘you could have guessed this all along’ moment for the fans.

Almost everyone thought that the soul stone, the last and the only Infinity stone yet to be revealed, was with Heimdall and that it will be revealed in "Thor-Ragnarok." Then came the curveball, "Ragnarok" came and went, still no soul stone.

This has already led the fans into a semi-crazy state, while some finding solace thinking that they would see it in "Black Panther."

But would Marvel really use their most anticipated reveal yet in a movie that is not so connected with their greater universe and has already gained enough hype around it? Imagine the "Infinity War" ending with the soul stone reveal, in an artifact that was shown all along these years. Cool, right?

Adam Warlock

The less likely, but all the more exciting possibility. Marvel is going to be making movies about new heroes in Phase 4. They have already introduced "Black Panther," with "Captain Marvel" and the "Wasp" coming up in the future. Would that be enough to hold on to the highly massive MCU fan faction?

Don’t they need someone with godlike powers?

Marvel has already teased Adam Warlock in the end credits scene of "Guardians of the Galaxy 2." While there are no official confirmations about Adam Warlock or about the casting choice, we all know Marvel’s secretive ways. They concealed Spiderman’s introduction in "Civil War" until the trailer release, is it crazy to think that they would pack in a big-Warlock surprise within "Infinity War?"

Wait, you need more evidence? How about the fact that in the comics, it was Adam Warlock who had the Soul Stone with him? Fangasm!

Let us know your comments about the theories and also tell us how you think the "Infinity War" could end.