Proton Shut Out Achievement
Proton Shut Out25
Prevent cannon attacks on civilian targets in the Island Meltdown missionWhen the Island Meltdown mission begins, you're given four power couplings to destroy. Start with the closest, and then work your way counter-clockwise. The initial power coupling might restore before you have a chance to take all out four, so as soon as you take down the fourth, head back to the first coupling while keeping your distance from the middle island.Once all of them are destroyed, head towards the center island and as soon as you're able to attack the large cannon, hover on the outskirt of the center island and position yourself to where you're just high enough to peek over the edge of the surface. You're able to stay mostly out of harm's way, and you can still target the cannon (the yellow target.) You'll occasionally be attacked by some AIM gunships or flying soldiers, so take them out as they appear, but stay hovering where mentioned and hitting the cannon with repulsor fire, missiles and the occasional unibeam. If you're quick enough about laying on the damage, you can end the mission, destroy the cannon and earn the achievement before the cannon gets a shot off.