Two astronauts are dead. And they represent one of my greatest achievements in a video game.
Of course it's terrible that the two Kerbals--an entire species of little green alien men who feel like an unholy combination of the Minions from Despicable Me and the Irken race from Invader Zim--are dead. I managed to keep them alive through disaster after disaster, spending hours ensuring to their survival in the cold black of space. Test missions were flown; probes collected scientific data; rockets would refuse to leave the ground and would explode or launch and then immediately tip over because the balance was wrong. These two died based on the collective knowledge of a thousand failures. And it was beautiful because they died crashing into the Moon.