7: psi emitter
You have to deposit a psi emitter to the right and have Kerrigan survive. Kerrigan is easy - hide her inside your base and don't use her. First, move all your buildings!! Make them all airborne immediately and fly them south. Block all entrances with a bunker and air tower. Start bunkering east - reinforce well, they'll attack you as you head that direction. Build a new command center by the crystals, and two bunkers, one by each east entrance. Air towers too. The turrets can see cloaked enemies, which they use a lot. Send out scouting parties, watching so you can pull them back to the bunker "death zone" when they're attacked.
Eventually you'll build bunkers right up to their main base in the east. Keep luring their forces into your bunker zone, and eventually you'll have bunkers right on top of their buildings and can send the tanks in to demolish them. When it's clear, drop the psi emitter and you're done!
StarCraft Walkthough Index