When Rhodey's War Machine armor is hacked. He's suddenly unable to control his own movement and is forced to watch as the armor attempts to kill his friend. At least Rhodey was well-positioned to warn Tony and able to communicate.
Imagine not only what Vanko could make Rhodes do, but what he could do to Rhodes simply by making the suit move in ways the human body isn't supposed to move.
The way the suit is built may incorporate measures to prevent this. It could still be flown into a solid wall or held underwater though.
The failed Hammertech manned power armor test run. This ended badly when the torso of the suit rotated 180 degrees (with a crack and muffled scream). Rivals The Dark Knight in terms of unseenBody Horror.
"I'd like to point out that that test pilot survived". Not exactly skipping down the street, one would wager. The test pilot's probably permanently paralyzed.
Having a fusion reactor powered by experimental palladium in your chest doesn't do very good things to the body. Just see the image on Tainted Veins.
This one comes when Fridge Horror kicks in: At the party, Tony is essentially drunk driving the most advanced weapons platform ever developed. And it's armed.
A bit of Fridge Brilliance, J.A.R.V.I.S. was keeping people safe until Rhodey showed up in the Mark II.