Dakboy’s right. You’re not going to understand this one completely if you haven’t seen most or all of the others plus the in-credits scenes. As noted before, Marvel laid the foundations for Avengers: Infinity War throughout all the previous movies. Just about everyone who was in an earlier movie showed up for this one and they brought back someone I wasn’t expecting but they got a different actor than before. They had an explanation for most of the characters who weren’t in it.
The movie follows on the heels of Black Panther, and like that movie, has a villain with a very valid reason for his actions. I’ve seen a couple of articles that say he could be the hero, just as I’ve seen articles that say that Odin was actually the villain for the Thor movies.
The previous times we’ve seen Thanos, it gave me the impression he was another of those villains that was doing bad things because he was a bad person. I’ll pick Enchantress from Suicide Squad as an example. She was imprisoned in the distant past with no reason specified in the movie that I can remember, so when she got free and found out that she and her brother weren’t being worshipped as gods any more, she decided to get back at the entire world. Kind of a petty reason.
Infinity War has a different Thanos. He’s seen first-hand what uncontrolled population growth will do when there’s finite resources, the same concern we have right now on Earth. For example, Lake Mead is estimated to go dry in 2036 and Las Vegas is already looking at getting a pipeline run to a different aquifer 260 miles away. But when no more water can be diverted from other areas to support it, Las Vegas will become a ghost town.
Thanos sees that happening on a universe-wide scale and he’s decided he has to be the one to prevent it. Not because he thinks he’s the only one that can see The Truth, as so many other deluded fanatics use as their justification, but because he’s seen the cost. Some of his “Children of Thanos” do fall squarely in the fanatic category because they see this as a holy mission, rather than the necessary mission that Thanos does.
We also see that when Thanos calls someone like Gamora “Daughter”, he means it. His necessary mission to save the universe has a nobility to it that’s not a feigned or self-righteous nobility, so if he takes you in, he cares for you, even if it doesn’t look like it.
But for everyone else, his actions are brutal. Death and destruction everywhere he goes. This accellerates as he begins collecting the Infinity Stones. Each one makes him more powerful than he already was, evidenced by the fact that he could touch each of them without being torn apart, like what happened to Carina in the first Guardians of the Galaxy movie (the slave of the Collector that decided enough was enough when she saw what the Power Stone could do). It shakes most everyone to their core, including, apparently, Hulk.
After jumping around to different parts of the galaxy to tell the story and show how all the pieces from the previous movies fit together, Infinity War culminates on Earth in a massive, very brutal battle. It’s not really a spoiler to say that a lot of people die because both Marvel and DC haven’t been shy about killing off characters (usually the villain) in their movies. But who dies and how it happens is brutal for the audience.
At this point, we have two more movies that will be released before the next Avengers film in May 2019. We have Ant-Man and the Wasp in July and Captain Marvel in March. It’s not directly related, but let’s throw in Deadpool 2 later this month. So, we’ll see how they fit into building to a resolution of where this movie ended.
If you haven't seen the movie yet, it's worth your time.