Yes. First, he’s unlocked his full power as the God of Thunder. He’s been defeated and has come back out of the proverbial abyss. Narratively, he’s nearing the end of his Hero’s Journey and his unlocked his full potential.
Second, if you saw that last scene, Thor threw the Storm-breaker at Thanos. By this time, Thanos had ALL the stones; he activated them to block the axe, but it still got through and stabbed him right in the chest. Thanos even told Thor that he should’ve gone for the head. If Thor did, there would be no need for Avengers 4 though, hence why.
Yes right now he’s the most powerful Avenger. My opinion is that in Avengers 4, he’s going to be the one who will ultimate physically kill Thanos (with an axe to head, as was foreshadowed by Thanos himself), and that Cap and Iron Man are going to sacrifice themselves to “snap” the gauntlet again to bring back all the heroes who were “snapped” out of existence (but not the ones Thanos killed permanently; they’re gone for good).