The Avengers filmmakers already admitted that he was virtually unbeatable. Except for one weakness, his only Achilles Heel. Infinity War was littered with clues and the new deleted scenes released yetserday only reinforce what is coming.
However Marvel just released some shocking new images today which give the biggest clue so far — and yet again it all points to one person. The latest Marvel Comics series, Infinity Wars Prime, opens with one of the greatest shocks in comicbook history. A mysterious character called Requiem has a powerful new weapon forged by the dwarves and uses it to decapitate Thanos.
In a later scene battling the Avengers and their allies, Requiem's helmet is shattered, revealing who it really is. This could change everything for the Marvel Cinematic Universe, too.
In the comics she is on a ruthless misson to acquire the Infinity Stones because part of her soul is trapped in the Soul Stone. Just as in Infinity War where Gamora became part of the orange Stone.
The Russo brothers already said that Thanos's only weakness is an emotional attachment.
To our knowledge he only has one attachment to anyone in the entire universe. Two of the three deleted scenes are about Thanos and Gamora and he even revealed that she had never escaped, he had let her go, unable to bring himself to stop her.
Gamora is his only weakness. Gamora has actually just killed him in the comics.