Thanos stared down at Gamora's broken form, mind in a turmoil. He turned to the hooded being, "The soul stone.' He said quietly. The thing he had sacrificed Gamora for. "Give it to me."
Red Skull looked at him steadily. "No."
Thanos frowned. "What do you mean, no?"
"I mean, this was a test. You failed."
"I…what? How?" Anger started to leak into Thanos' voice.
"You don't have to have a pure soul to be able to wield the soul stone. But you do need to, metaphorically, have a soul. You claimed to love your daughter, yet you threw her off without a second thought. You have, as humans put it, sold your soul to the devil. The devil, in this case, being your own mind."
Thanos' fists were clenched, anger clouding his vision. His daughter…gone, and for nothing.
Red Skull walked over to stand beside him, looking down at Gamora."You know…" He said quietly, "We're not so unalike, you and I. We both wish to create a better world. However, a word of advice. Don't go up against humans."
"Why not?" Thanos asked, not really listening.
"Because I opposed a human army once, and failed miserably. Their lives are fleeting, yet it only makes humans all the more determined to not waste them. And unfortunately for you, I doubt Peter Quill has the same moral compass as Steve Rogers."
Thanos frowned." What do you mean by that?"
"He killed his own father." Red Skull said bluntly." He gave up the power of a Celestial because Ego killed his mother."
He paused. Under the hood, Thanos could see something resembling a smile."You've killed the woman he loves. He'll happily tear you to shreds."
With that, he disappeared, leaving Thanos alone.