Squad time! This is very easy if you're careful and have a plan. Mine worked very well and here it is. First, take the IFV your psychic captures to the northeast and eliminate the two GIs guarding the small base. Capture the engineers one at a time with your other psychic (not controlling the IFV) and take the buildings. Now you can build a spy, and just one spy will do. If you encounter another IFV capture it, as we will want two for the following operation. The northeast corner of the base the president is hiding out in has one weakness that I know of: The northeast wall has no prism towers so there is a small area where you can assault the wall. There are two guard dogs and a GI who patrol outside this wall as well and you will want to eliminate them for the purposes of having your spy remain stealthy. Once the dogs are destroyed and there is a breach in the wall, send the IFVs to their demise and sneak your spy into the power plant. The annoying prism towers will not be offline and you are free to mind control the seal near the president (the one on the side you are coming from), he will be killed almost instantly at which point you can mind control the president himself.