Red Skull: I... there's no way you just did that.
Thanos: now... when exactly do I get the soul stone?
Red Skull: I... you... NEVER! never, you idiot! why would you even think that wold work??
Thanos: you said if I sacrificed what I loved most, the stone would be mine...?
Red Skull: right. yes. I said that. but that's a logical contradiction, because if you sacrifice anything for the stone, it means you value the stone more, so nothing you sacrifice can ever be what you value most. how could you be a centuries old war tactician and dictator and not understand this?
Thanos: how am I supposed to get the stone then?
Red Skull: *string of German profanity* you don't! you can't! it's not possible! this is whole setup exists to make you realize your quest is fruitless and make you give up on the stone in favor of what actually matters to you. but apparently that's nothing because you're a monster! this is literally one of the most well know and basic tests of character in the universe. like this plot shows up most in children's stories, this is a test for a child, children who've been alive for a minuscule fraction of your existence could and have passed this kind of test thousands of times before. I have literally never, ever, in my supernaturally-extended life, seen anyone fail it so spectacularly as you before. me even being the one to present people with this moral dilemma is meant to be dramatic irony, because I'm a Nazi and that's bad or something. I'm a Nazi and I'm morally appalled by you right now.