Thanos has an obsession with death – in more ways than one. Not only does he crave death itself, but he is also in love with the cosmic entity known as “Death” or “Lady Death” – Marvel’s all-powerful Grim Reaper, so to speak.
As a result, most of his plans revolve around death in one way or another and, while we can’t see the living embodiment of death appearing in the Marvel Cinematic Universe (and therefore no attempts to please her by Thanos will occur), what may happen is that Thanos realises he is unchallenged by the meagre might of the heroes present and, as such, might give up based on the fact that he knows he will prevail.
It sounds odd, but that’s just what Thanos is about. If he comes to the conclusion that to challenge Earth actually isn’t actually “to court death”, he might stop in his tracks and move on.
That what most people don't realize about Thanos is that, Thanos can beat Himself. Thanos weakness is that he secretly does not want to win. (EGO,PRIDE) Has a subconscious desire to lose. The man has an obsession with Death death. The Grim Reaper of the Marvel. and wishes to please her.
He basically arrange for himself to be defeated because deep down he knows he doesn't deserve to win. EGO. Wants one thing you can hurt a man's pride??. EGO.
Batman as always is smarter than people think.. Batman can beat him by simply talking slick to him. By stroking his EGO. Hurt his pride. The End.
Batman can say some shit to him like.... Your the most powerful Being in this Universe, But yet your methods of killing someone, is some what truly amateurish and pathetic. A human can do better than you...
an Example of what I am talking about.. What Sentry said to him.