Mind... Blown... FOREVER!

Rating: 10/10 (27 April 2018)

This top part is spoiler-free
I'm not sure where to start with this movie. I've seen other reviews for this movie that had titles like "better than the hype" and "I need a therapist"; I can honestly say the same things after watching it for myself.
The action was almost nonstop, but still fun and engaging nonetheless (although I still appreciated the few slow moments it had). The plot was straightforward and spot-on, predictable in many places but mind-blowingly unpredictable in others. There was a small amount of character development, which is still impressive considering how this movie has way too many characters (but the writers and directors were able to pull it off somehow). There was a lot more humor than I expected, which not only made the movie even more entertaining, but it also exemplified the wonderful chemistry between all the crucial characters.
Thanos made a fantastic villain, easily the best one since Loki. And something that impressed me about this movie is that even Thanos' top-ranking henchmen were insanely powerful, even when compared to the other major villains throughout the franchise. Even the thousands of mindless soldiers Thanos sent on everyone (more particularly during the battle of Wakanda) seemed to pack their punch. It was because of these aspects that we actually had real concern for our heroes, because they were all banding together to face off an enemy, and an army, that was seemingly invincible (especially considering how much power Thanos has with his Infinity Stones).
One thing I will forewarn, however, is that if you're trying to figure out the plot and uncover the spoilers just by watching the previews, you might be on the right track, but the trailers are also fairly misleading.
SPOILERS BELOW. Do not read unless you've already seen it or just simply don't care about seeing it.
Out of the cameos that happened in the movie, Stan Lee's was funny as always (although more brief than usual), Peter Dinklage's appearance was somewhat strange considering how he's a little guy portraying a giant (in my mind, he's still just Miles Finch from Elf), but the one that permanently blew my mind was the Red Skull's appearance on that planet with the Soul Stone (I was disappointed to find out later that he wasn't played by Hugo Weaving again, but at least this answers the epic question as to what happened to him at the end of Captain America: The First Avenger).

The Russos had previously denied the theory of this movie having a serious cliffhanger ending that will be resolved in the next movie (like Harry Potter, Twilight, Hunger Games, Hobbit). I'm not sure whether to call them liars, because this movie's ending can either be seen as a tragic end or the worst heartbreaking cliffhanger in history - Thanos wins by snapping his fingers with the completed gauntlet which disintegrates half of all living souls in the universe into ash.
However, here's the ultimate kicker: Earlier, Doctor Strange mentioned that, out of the approximate three million possible endings for the infinity war (forgive me, I forgot the exact number he stated), there was only one way for Thanos to lose. After Thanos successfully obtained all six stones and obliterated half of all life, Strange mentioned that it is going according to plan. In that case, I would expect Doctor Strange to be the most crucial player in the next movie alongside Captain Marvel, who was teased in the post-credits scene.
Out of all the character deaths that happened in this movie, I can expect only a few of them to be permanent. Those who were killed prior to the end (Heimdall, Loki, Gamora, Vision(?)) I can expect to be permanently dead, but those who were disintegrated after Thanos' finger-snapping (Bucky, Black Panther, all the Guardians except Rocket and Nebula, Spider-Man, Nick Fury) I can expect will return for the sequel somehow, according to the plan Doctor Strange had in mind (but the sequel might have even more permanent deaths). Besides, Marvel has already planned sequels for Guardians of the Galaxy, Spider-Man, and Black Panther.