Trivia: When did Thanos first appear in the Marvel movies?

We're still hung up on Infinity War! So Thanos first appeared in the comics back in 1973's Invincible Iron Man #55, but when did he first appear in the Marvel movies?

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Trivia: Domino is associated with which superhero team?

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Trivia: Who or what has Thanos fallen madly in love with in Infinity Gauntlet?