UFO Enemy Unknown on Superhuman difficulty. I was getting through the game quite handily, albeit with high casualty rates, but once I started encountering the Ethereal race, my guys stood no chance to their psy attacks. I ended up avoiding any crash site missions containing Ethereals. Unfortunately, the alien base on Mars, during the end game, was full of these aliens and I suffered a humiliating defeat before half my guys even made it out of the transport ship. They were just getting mind controlled and killing their teammates. I tried it so many times with no difference. One day I might start a new game and try again.