In case the title wasn't enough this will have SPOILERS. If you haven't seen it yet, you definitely don't want to read any spoilers, trust me.
As promised this will be far more fleshed out then the spoiler free review. First off, the movie is fantastic, it has become my favorite Marvel movie. Many fans were speculating how tough Thanos could possibly be, "just throw Hulk at him" was something many were saying and I do believe that Russo brothers were aware of this and settled the matter right away. I think it answered 2 important questions, yes Thanos is POWERFUL, and the best way to neutralize the Hulk is overwhelm him with power before he has a chance to get angry. I think many people were disappointed with the Black Order (Thanos' generals) and the fact I have to point out who they were points it out. They didn't have much dialogue and weren't addressed too much given how much this movie had to accomplish. I still loved having them there, and felt there power levels were just right, not too powerful that made the whole mission too daunting, and not too weak that basically defeats the purpose of him even having helpers.
Some people also had issues with it not being all characters teaming up on Thanos at the same time, but I do believe that will come later, and them having multiple little groups was the best way to do this. While I did want to see Cap reunite with Tony, there was some great chemistry happening between Stark and Strange. Throw Spiderman into the mix along with some of the guardians of the galaxy and you've got a great team up. I didn't care for the other team up as much, which was basically the rest of the avengers, along with Groot and Rocket towards the end. I felt majority of the chemistry and character relationship was built around the group on Titan.
Thanos has become one of my favorite villains, I was so glad they gave him a backstory or at the very least an explanation as to why he believes what he believes. And that was the thing I had assumed going in. I didn't think they would even take the time to touch on that. His motivation to prevent extinction by genocide was working for the species he had already done it to. He was a villain who TRULY believed what he was doing was right. His power level was great, and above all else his dialogue was epic and that's what really stuck with me after the movie finished. The dialogue in the movie overall was just great to begin with. When he was fighting Tony he had said (paraphrasing) "after I'm done, half of humanity will still exist, I hope they remember you". There was this sense of respect that Thanos showed Stark that was really cool to see. Also when Iron Man threw everything he had at Thanos and he just responded with "all that for a drop of blood" it just further drove home how powerful he was.
Probably my favorite action scenes were the ones on Titan, seeing Guardians + Strange + Iron Man + Spiderman had great synergy (despite Star Lord losing his cool). The whole fight especially where they combo there abilities together was such a comicbook kind of scene it made my inner child all giddy.
Finally, one thing I was not expecting to love was the emotional scenes. I expected the movie to be action start to finish and I would've been ok with that. I didn't expect to be emotionally devastated. Seeing Loki die at the very beginning was heart wrenching and again solidified to the audience that were in for a very dark ride. When they showed the slaughter of Gamora's people transition into her begging Star Lord to kill her if it came to her being captured by Thanos was another one. Another piece of great dialogue was when Gamora mocked Thanos for crying only for Red Skull to respond with "the tears aren't for him". The movie just refused to let you get a breather because as soon as she is sacrificed the ball gets rolling for the final act. And my my what a final act it was. Seeing the two battlefields play out was great. The battle between Strange vs Thanos, Thanos vs Stark, as well as the fight on Wakanda were great spectacles Strange vs Thanos in particular. But after that was all said and done and Scarlet Witch is forced to kill her own husband only for Thanos to bring him back to life, and kill him again anyways. This movie controlled the emotion of its audience from beginning to end. When Peter Parker is crying that he doesn't want to die in the arms of his psuedo parent (Tony Stark) the whole theater was silent. I can't remember the last time I've left a Marvel movie with a sense of hopelessness. Even Civil War I left with a sense of satisfaction that the team would eventually get back together. Now I know that those that disappeared in ash will be back, I mean they all have sequel movies for a reason but it's still powerful to see. Granted I don't see many movies especially not in the theaters, but I've never seen an audience laugh, gasp, cry out, and silent all at the same time. I've never finished a movie and have it go to credits and the entire audience just stunned in silence. With time, the "critics" may pick this movie apart for stupid or even legitimate concerns, but I will never forget this feeling, the feeling of awe as i saw my favorite heroes fight the biggest bad of the universe.