From the film's opening scene he already has the Power Stone, and by the time the opening title plays he obtains the Time Stone as well. But wielding two Infinity Stones does not make him the post powerful villain in the Marvel Cinematic Universe. He already had that distinction before his hunt for the stones because of his strong will.
"Thanos] is almost unstoppable in the film," co-director Joe Russo said on the film's commentary track, prompting co-writer Stephen McFeely to elaborate.
"He's got the strongest will," said McFeely. "I mean, thats one of the things we always thought is that he's not dangerous because he's got the Stones, he's dangerous 'cause he has the will to use them."
"He wont quit," added Russo.
The creative team from the movie previously elaborated on Thanos' strength, revealing that he didn't need — nor did he even use — the Infinity Stones to defeat the Hulk. Instead he handily beat him at his own game, with brute strength, in the film's opening scene.
"Here you see the early establishment of just how fearsome Thanos is even without, he's got one stone here and I don't think he's even using it," McFeely said.
"He's not using it," Russo said. "This is to show that Thanos, the Genghis Khan of the Marvel Universe, he's unbeatable in 1-on-1 battle. He's conquered thousands of worlds. He's a much more polished fighter than the Hulk, and Thor, and Loki."
"We want to announce Thanos as the biggest villain in the MCU, he takes out the previous reigning champion, and by defeating Hulk relatively savagely and easily, hopefully, there's a sense of dread over the course of the rest of the movie for anyone who will come up against him, and so that's just sort of a scene design," McFeely said.
The film did a good job of stringing viewers along, presenting a false sense of hope that maybe the Hulk would return or that Thor would actually manage to kill Thanos before he achieved his goal. Unfortunately for the Avengers, that did not happen.
We'll have to see how Earth's Mightiest Heroes manage to surpass Thanos' own willpower when Avengers 4 comes out next year.
Avengers: Infinity War is now available on digital HD, and will be released on Blu-ray and DVD on August 14th.