Avengers: Infinity War completely retools Thanos’ character from the comics. In contrast to the insane tyrant who wants to destroy as much as possible in order to win the love of a very special lady, the MCU’s Mad Titan sees himself as the savior of the universe, as he only wants to half all life as an extreme solution to overpopulation problems.
For the most part, this is a canny choice for the movie, as it makes Thanos a truly compelling antagonist. However, it causes problems, as the previous appearances from the character in the MCU had been done with his original comic book personality in mind. In fact, the changes are so vast that they create a massive plot hole when it comes to the backstory of his adoptive daughter, Gamora, as established in Guardians of the Galaxy.
In the read-out of Gamora’s details when she’s arrested by the Nova Corps, it’s stated that she’s the “last survivor of the Zehoberi people.” Thanks to a flashback in Infinity War, we now know this isn’t true, as Thanos only killed half of her race. Not that this isn’t a tragedy, but that far from makes Gamora the last of her kind. I suppose we can wave this away as an error in the Corps’ systems, but it’s clear that the plans for Thanos changed over time.
Gamora’s backstory isn’t the only thing that’s affected by the changes to Josh Brolin’s character, either. The Mad Titan’s very first scene in the MCU also looses something in light of the revelations made in Avengers: Infinity War.
If you’ll recall, at the end of The Avengers, Thanos’ henchman The Other tells him that to challenge humanity is “to court death,” causing a sinister smile to spread across the big guy’s face. This was a clever double entendre that alluded to Thanos’ infatuation with Lady Death in the comics. Now that we know this isn’t a thing in the movies, though, we’re not really sure why the Mad Titan found it so funny.