I don't think the impression was ever than Thanos alone was an unstoppable bad ass. I feel that he appears that way (in both comics and the movie) because he doesn't just like to win he likes to conquer and decimate, but we're still dealing with a guy who LIKES to fight, and is EAGER for someone to actually fight him to a draw or worse. All of his children were very lets keep this short and to the point kind of villains, and they retreated and strategized ways to do it without a "fight", but all of Thanos' engagements were very come at me bro, even against enemies he didn't understand or know. He doesn't even really "rely" on the guantlet or the stones until he has to. The only scenario in the movie that actually "challenged" him was the one that involved no fighting at all (Gamora) and they sold the fuck out of his emotional response to that. He didn't give a shit about all the necks he broke.
I would theorize the way they wrote the final Thor encounter was that quite literally Thanos would happily give Thor the first shot, even with a new toy that could possibly end him, because I think more than anything he wants is for someone to show him he's not absolutely right about everything. He probably still entertained, even then, that this guy who definitely talked a lot of shit was about to back it up the way no one else he had to fight did, even cap, and star lord, and strange and all the other "leaders". And when Thor quite literally blows it, he realizes he was right, and its time to pull the trigger. A big part of how the comic is actually resolved is not so much just because they stop him blow for blow, but because they reason him into changing his mind about everything, war, life, death, family, friendship, etc and he finally relents.
THey've done freakishly powerful villains like Dormammu and Hela and Ultron who didn't really care about the battle, they only cared about the end game, those are the villains you have to just "checkmate" because they won't stop, they just want to win. But I got the expression just from that first scene where Thanos' guys are casually hanging back while he's going to work on a bunch of Asguardians and the god damned Hulk that Thanos' conquest isn't just about winning, its about proving a point, and after he successfully proves he's stronger than everybody, then its like, right, here's my victory lap, bitches. get erased.