Even if he's just relying on his own natural abilities, Thanos is one of the strongest beings in the Marvel Cinematic Universe. Throw the Infinity Stones into the equation, and he unquestionably becomes Powerhouse #1 in this franchise, hence why he was able to able to take out the heroes in Wakanda at the end of Avengers: Infinity War without breaking a sweat. However, you probably noticed that Thanos didn't go out of his way to kill all of Earth's Mightiest Heroes, and that's because as he came came closer to accomplishing his goal, he was less concerned with taking lethal measures with his opponents. According to Marvel Studios Head of Visual Development Ryan Meinerding:
The plan of getting all the Infinity Stones is putting [Thanos] in the position of being so powerful that he is sort of calmer, more single-minded, and more reasonable. He is not necessarily worried about killing the heroes. As long as he ends up with the stones, he can accomplish what he wants to.
It's ironic that for a warlord so determined to eliminate half of all life in the universe, Thanos didn't feel the need to snuff out most of Earth's Mightiest Heroes when Avengers: Infinity War was wrapping. But, as Ryan Meinerding pointed out in the book The Art of Avengers: Infinity War (via Screen Rant), by that point in the movie, with five Infinity Stones in the Infinity Gauntlet, he didn't feel the need to snuff the life out of them. Getting that last Infinity Stone was all that mattered.
At this point in Avengers: Infinity War, Thanos likely looked at the heroes standing in his way like ants to be swept away. Just look at how he toyed with Captain America. Thanos could have incinerated Steve Rogers in an instant, but instead he kept pressing down on the hero, curious to see how long Steve could hold back his hand and then taking him out with a swift punch to the face
The big exception to Thanos' no-killing approach on Earth, of course, was Vision, everyone's favorite multi-colored, British android. Thanos' minions tried their best to take the Mind Stone from Vision, but as the old saying goes, if you want something done right, do it yourself. Scarlet Witch succeeded in destroying the Mind Stone, but thanks to recently acquiring the Time Stone, Thanos easily reversed Scarlet Witch destroying the Time Stone and pulled it from Vision's head, leaving his now-gray corpse behind.
Of course, all of Thanos' efforts in Avengers: Infinity War were to bring forth death, in a matter of speaking. Having seen overpopulation destroy his homeworld Titan, Thanos set forth to eliminate half of all life in the universe in order to prolong available resources and achieve true balance. With the six Infinity Stones, he was finally able to accomplish that and retire on a serene planet afterwards.
We first met the MCU's version of Thanos in The Avengers mid-credits scene when he smirked at the camera after his minion, The Other, warned that to battle the Avengers would be to court death itself (alas, we won't be seeing this version of the Mad Titan professing his love for the personified Death). Thanos briefly returned in Guardians of the Galaxy to berate Ronan, who he'd tasked with finding the Power Stone, but that appearance was also basically just a cameo. Still, there was definitely a sense that Thanos was not someone to be trifled with.
It was in Avengers: Infinity War that we finally saw firsthand was he was capable of, and he certainly had no problem leaving death and destruction in his wake early on. The movie opened with the half of the survivors from Asgard dead at his and the Black Order's hand (Loki and Heimdall included), and we learned later from Thor that the Mad Titan ravaged Xandar to obtain the Power Stone. When you're starting your Infinity Stones quest, drastic measures are required.
Let's also not forget that to add the Soul Stone to his collection, Thanos had to kill Gamora, his "favorite daughter." As the Red Skull revealed, the Soul Stone can only be retrieved by someone sacrificing something they love, and contrary to Gamora's belief, Thanos truly did love her, albeit in a twisted way. Pushing Gamora off a cliff earned the antagonist one orange rock.
By the time Thanos arrived on Titan to fight Iron Man, Doctor Strange, Spider-Man, Star-Lord, Drax, Mantis and Nebula, he'd fallen into a more calmed state, though he wasn't quite invincible yet. The heroes nearly succeeded in overwhelming him and pulling the Infinity Gauntlet, but once Star-Lord went off book after learning Gamora was dead, everything went to hell. Thanos did threaten to kill Iron Man, but that was only so Doctor Strange would hand over the Time Stone.
As things stand now, Thanos is enjoying his retirement and presumably not interested in battling superheroes anymore. And even though the Infinity Gauntlet was damaged after he snapped his fingers and carried out genocide, the Infinity Stones appear to still be intact, thus making him still the most powerful being in the universe. But he can't fully relax just yet.
It's expected that the surviving heroes will somehow reverse Thanos' action in Avengers 4 and bring back the people that he turned to dust (well, the heroes, at least). How they'll do that remains unclear, but with Josh Brolin confirmed to be reprising the Mad Titan in the Phase 3 capper, one can assume that eventually he'll be drawn back into action and do whatever is necessary to make sure his will on reality isn't changed. Maybe now he'll be willing to take a permanent course of action towards those still opposing him.
Avengers 4 opens in theaters on May 3, 2019, so stay tuned to CinemaBlend for continuing coverage. In the meantime, look through our Marvel movies guide to learn what else the superhero franchise has in development, or you can check out our 2019 release schedule to see what non-Marvel Cinematic offerings come out next year.