Ended up rewatching Avengers Infinity War and Endgame again, after watching the first two episodes of WandaVision.
I still prefer Infinity War -- I think it is more remarkably consistent in tone and has this feeling of dread that permeates from the very beginning of the film, where the clashes between Thanos' agents and the heroes feel particularly lethal. (I mean, you have an opener that is just shocking in tone and approach, including the perma-death of two major characters, setting the stage for the rest of the film as well.)
You also just see these actors and actresses playing characters they know super-well, so they almost seem to be inhabiting their skin.
You also see a more mature Thanos. Once he gets the first two stones, he seems to retreat from wearing his battle armor (as it doesn't do much for him anyway). But he is taking an active role in his own destiny, after presumably watching his agents failing multiple times. He realized at some point that if he is going to be the hero of this story, he needs to step up... and he does. There is a kind of world-weary acceptance that this venture will rise and fall on his own competence now, his own strength, and both his victory or failure will belong to him. I really like that he always seems calm, and incremental in his progress. He feels like the specter from "It Follows" -- just marching forward, same pace, never stopping, never rushing, getting each piece he needs one at a time. The later comment about, "I am inevitable" -- yes, exactly, and especially by the last moments of IW. His greatest trial is getting the Soul Stone, and it amounts to sacrificing the one thing he loves.
He's just such a fascinating character here, because he's not all "bad" -- he is a hard father but a just one, for example. "You're strong. Me, and generous... me. But I never taught you to lie. That's what you're so BAD at it," he says to Gamora at one point, and he's right. (Later, Nebula says of him that her father is many things, but a liar is not one of them.) he's basically the ENTJ Lawful Evil villain. He will be honest, and be disciplined, and follow rules, and remain fair (he reveals he had offered genocide to Titan, his own planet, but sparing no one... rich and poor would be treated ALIKE) -- but he has no problem with genocide in the first place, is willing to torture one daughter and sacrifice another to fulfill his destiny, and so on.
And it is really clear that he does care for Gamora, in the many scenes they have together. He dotes on her. It is what makes the bit with the soul stone so tragic. (And yet even then, you have a nice counterpoint between this scene -- where he sacrifices someone else to get the stone -- and the comparable version in Endgame, where a different character sacrifices themselves so someone ELSE can get the stone. Thanos abandons love for destiny; the other abandons life out of love.)
The conflict sequences are just so inventive, especially the one on Titan. I mean, I just watch this film, and it is so obvious that each scene was gone through with a fine-tooth comb, then combined and compiled with the other scenes, to create one story arc where things mesh. (like tony's sequences and the fight sequence with dr. strange, but really all of it.) And THEN they work on the details of the emotional journey. Line readings. Facial expressions. Nuances. Dramatic pausing. Every moment feels dire; it's never clear where the film is going or who might survive it. it's as much a study in craftsmanship as anything else, how to put together a film that has a lot of special effects without losing the human drama -- it's all to support the human drama. Everything is just so set up. Like Strange telling Tony he would immediately sell him out to protect the Time stone, so when he offers the stone for Tony's life... you know something bigger is at play. Or the parallel line craftings regarding Vision and Wanda, mirroring their early exchange: "You could never hurt me. I just feel you." Vision's line reading is so perfect when he tells her it's not fair, but she's the only one who can do what has to be done. (Which is correct -- because in the movie continuity, her powers came from the Mind stone, so that's why they operate on a similar frequency.) I'm kinda floored just watching how meticulously it was all put together. And then it's unbelievably tragic, with Vision passing once as a hero, but you know Thanos has acquired the Time stone, so it becomes utterly tragic a minute later as he passes as a victim. If you are paying attention, you already know how that bit will play out.
What really keeps Thanos from being a complete villain is simply his methodical, paced, impersonal approach -- he is solving a problem, and he doesn't seem to bear animosity towards particular people. He even seems to treat Tony with respect, even while preparing to finish him off. it gives him an air of nobility (despite the horrible thing he's doing) that makes the film about his hero's journey, even while you don't want him to win. You also understand his logic, even if it seems cruel and maybe eventually not foolproof (as won't the universe reach this point again in the far future?)
Endgame is a bit more uneven in its tone and approach, although the first and third portions are stellar (examining the human impact of the snap and the inability of the Avengers being able to fix things, and later then the final battle sequence that lasts a good 20-30 minutes). But it still typically has the connections to all the early films. There are a multitude of lines that have meaning if you have seen earlier films. Some (like "To your left") are more obvious. Then there are others, like when Hawkeye is harried with the Gauntlet and Black Panther arrives and says his name to win his attention/trust; back in Avengers: Civil War, when they meet for the first time, Hawkeye introduces himself in a conflict ("i'm clint") and BP responds with, "I don't care." But now he's using his name. Nat's arc is a lot more obvious on repeat viewings. And so are Tony's and Steve's. It's all tracked and set up, in there. So maybe it's a surprise on first viewing, but later viewings support the journeys. Thor pushes his axe into Thanos' chest in IW; it's reversed in Endgame. So much stuff like that.
Still, this is an earlier Thanos. He's full of hubris and aggressive, rather than having the internal centeredness and sense of purpose of Infinity War. He's more violent than he needs to be and seems to take pleasure in cruelty -- where notice how by the final piece of Infinity War he almost becomes gentle, all the ways he doesn't kill the Avengers and even cradles Wanda's head in sympathy at one point. in Endgame, he's also shocked when he loses; he bought into his own myth and competence and is completely taken aback, defeated. it is like that 4-5 years of futility that shaped him into a more centered personality leading to Infinity War hadn't yet happened, and here it results in his defeat.