Tony's capture, imprisonment, and hazy surgery. Being held hostage in a part of the world where a lot of people will hate your guts, no one knows where you are, and these people are more than ready to execute you slowly. The scene of the terrorists filming their demands is quite chilling.
Made worse in that when he's being dunked under water, the car-battery that's keeping him alive is shown sparking and nearly shorting out, meaning that Tony's not only being nearly drowned, but suffering mild electrocution and cardiac arrest at the same time!
The Ten Rings' invasion of Gulmira.
Stane's paralyzing Tony and pulling out his arc reactor, all the while never dropping his Affably Evil personality and casually telling him that he's going to murder Pepper before leaving Tony to die a slow and painful death of shrapnel in the heart.
Consider Obadiah Stane and his motivations in the wake of Cap 2's Hydra reveal. Hydra said that accidents happen. The easiest way for them to set up a murder as an accident would be to have an inside man Howard trusted. Add to that Stane selling weapons to terrorists being exactly the kind of thing Hydra would do to sow disorder and fear and its wholly possible That Obadiah was a Hydra mole.
Iron Man 2:
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.
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.