“To court Death”
They changed Thanos’ character quite a bit in the film adaptation of the comic book supervillain. Although the essence of Thanos remained relatively untouched, some of his backstory was removed to stop the movies from lasting over six hours long (shame).
During the credit scenes of The Avengers, we can see Thanos’ aid telling him that “to challenge them is to court death.” This might not seem like an odd line, but it’s actually referencing Thanos’ motives in the comic book storyline, namely, to literally court (marry) Lady Death. Don’t worry if you missed this. We did, too.