Captain America: Red Skull grabs an Infinity Stone with his bare hands, gets his face melted off like in Raiders of the Lost Ark.
Guardians of the Galaxy: “Yeah, Infinity Stones are not to be fucked around with. If you’re anything less than immortal, touching it for more than a second will make you explode. MAYBE if you got a couple of people to share the load, you could hold it for a minute or two, but even then if you push it too far your head will pop off like a soda bottle.”
Thor 2: Jane Foster absorbs an Infinity Stone into her bloodstream, sees the whole of the universe, develops defensive superpowers, goes for days where her only negative side effects are a fever and occasional fainting.