The largest film in all of the MCU, Avengers: Infinity War brought everything together, and in doing so, events flew by faster than Loki's screen time. Hopefully, this list will be able to clarify and highlight anything the first time viewer might have missed.
16. Hulk Smashing Into the Sanctum Sanctorum
As Marvel fans remember, most of Avengers: Infinity War is based off of Jim Starlin's 1991 graphic novel The Infinity Gauntlet. In that story, it's the Silver Surfer who smashes through the roof of Doctor Strange's Sanctum Santorum and announces that Thanos is coming in utter feat and terror. The Silver Surfer, however; is owned by Fox Studios, and with the Disney acquisition deal yet to come into fruition, the MCU decided to just replace the role with the Hulk.
15. Peter Parker's First Spider-Sense
Spider-Man: Homecoming might have done a lot in reimagining the role of Spider-Man in the MCU, but it's on the bus scene that we first see Peter use his famous "Spider-sense," the power that allows him to sense when danger is fast approaching. As we see on the bus, the hair on his arm rises up once Thanos' Black Order arrives.
14. Stan Lee's Cameo
It's one of the fastest cameos yet, but it can be seen clearly that Stan Lee is the bus driver in the same scene where Peter Parker makes his entrance into the film. At the end of Guardians of the Galaxy Vol. 2 the end credits scene revealed he actually works for the Watchers in looking over Earth's Mightiest Heroes.
13. The Nova Corps is Gone
When Infinity War kicks off, Thanos has already destroyed Xandar and taken the Power Stone, meaning the Nova characters played by Glenn Close, John C. Reilly, and the rest of the Corps, are all dead before the film even begins. The decimation of the Nova Corps would actually set up a future Nova film, with the last surviving member out to take his revenge.
12. Valkyrie Had Already Escaped
Before Thanos could strike Thor and decimate all of the Asgardians, Valkryie, played by fan-favorite Tessa Thompson, had already escaped with some other Asgardians, as the directors revealed. Her current whereabouts however, would reveal too many "spoilers" for future films.
11. Thanos Getting a Face Full of Web
Thanos getting his face full of Spider-Man's webs while team Iron Man is trying to wrestle the Gauntlet off of the mad villain on planet Titan happened in the 1991 Infinity Gauntlet comic as well, referencing a classic distraction move from the friendly neighborhood hero.
10. Thanos Torturing Nebula
Also a reference to the 1991 Infinity Gauntlet comic, Thanos torturing his daughters is old hat for the mad titan, especially when that daughter is Nebula. It might have been more robotic-based in the film, but Thanos straight up burns away Nebula's flesh in the graphic novel. He does worse to others however, as he snaps Wolverine spine and breaks Captain America's neck with a simple backhand slap.
9. Wong Doesn't Abandon Everyone... Sort of
Okay, Wong does abandon everyone when it comes to the fight against Thanos, but leaving the Sanctum unguarded is actually a pretty big deal. Remember the demon from the first Doctor Strange film, Dormammu? He wanted to destroy the whole universe. Thanos just wanted half. Wong was simply reordering his priorities.
8. Tony Stark Had Been Carrying Steve Rogers' 'Civil War' Phone Everywhere
Despite losing Civil War, Steve Rogers gives Tony Stark a flip phone, now that he's off the grid, in order to reach him whenever he changed his mind. In a heartfelt callback to the previous Avengers outing, Tony reveals to Bruce Banner that he still carries the phone Rogers gave him around with him everywhere he goes, as he was just on a run with Pepper Potts when he got called in.
7. Steve Rogers Sees Bucky for the First Time Since the '40s
Steve Rogers and Bucky have shared the screen for awhile now, from Captain America: Winter Soldier to Civil War, but following his rehabilitation, their meeting in Wakanda is the first time Steve and Bucky have truly seen each other since his de-brainwashing. It might have been a quick "welcome back" of a greeting, but it was the first time Steve and Bucky had seen each other clearly since they both "died" in WWII.
6. The Iron Man Suits Are the Only "Avengers" Left
Tony Stark might have won Civil War, but he lost the Avengers. The goal of uniting all of Earth's Mightiest Heroes fell apart, and with Steve Rogers running around on his own with Scarlet Witch and Falcon, Hawkeye and Ant-Man on house arrest, Hulk and Thor in space, and the Vision running away with Scarlet Witch, that left just Iron Man and War Machine as the only two "Avengers" actually left, as the film showed War Machine being the only Avenger to answer the general's call.
5. The Red Skull is Back
In one of the most surprising cameos of the film, the Red Skull was brought back as the protector of the Soul Stone, but his simple cameo wasn't just a teaser for fans. It means the Red Skull is permanently back in the MCU, in whatever form or function they wish to take him next.
4. Heimdall is Gone, But Thor Can Summon the Bifrost Now
Heimdall, the Asgardian played by Idris Elba, was murdered by Thanos right away, but he possessed the ability to summon the bifrost, the bridge that was able to transport people around the universe. When Thor is forging his new axe, Stormbreaker, Eitri, the Dwarf King, reveals the axe may be able to summon the bifrost. How convenient.
3. Anyone Who's Anyone Knows Who Tony Stark is
Thanos might have been watching Earth for years, as it's the location of a fair amount of the Infinity Stones, but he didn't seem to be familiar with most of Earth's Mightiest Heroes. Someone he does know however, is Tony Stark. Maybe it was just Thanos' business to know all of his greatest threats, but it's also possible that Stark's efforts have also placed his name on a universal scale.
2. Calling Captain Marvel
Knowing that Captain Marvel takes place in the '90s, early in Nick Fury's career, it'll be interesting to see what the hero has been doing all these years we could have used her help. With the addition of time travel theories and these weird old-tech meets new-tech pager device, it may lead to Captain Marvel being stuck somewhere in time. That, or out in space. Either way, it's clearly her logo on Nick Fury's pager at the end of the end credits scene.
1. The Infinity Gauntlet is Broken
Shown in an incredibly quick shot at the end of the film, the Infinity Gauntlet has been completely destroyed after being used to wipe out half of the universe. Thanos, either somewhere in the universe or trapped within the Soul Stone (with or without Gamora), is shown resting by a lake house, and next to him is the Gauntlet, completely crushed and shattered. Whatever the remaining Avengers cook up for Avengers 4, it'll have to be without that Gauntlet as it exists now.
Avengers 4 is set for release May 3rd, 2019.