[Nothing]

But I mean, if you're asking for total consistency then the soulstone should have killed Clint when he held it in his hand after Black Widow's sacrifice on Vormir. Clint is just a regular dude with a bow. Certainly shouldn't be capable of holding an infinity stone. Yeah yeah, I know it's different franchises entirely, but the same sort of principle is in operation. The amount of power any given character has at any moment is always very convenient to the story.