How to Beat Destroying the Dark Energy Reactor

The final boss fight involves destroying the Dark Energy Reactor. The reactor is protected by several energy conduits that Breen will activate. Your task is to use your supercharged Gravity Gun to grab and launch the energy balls (Dark Energy Orbs) that Breen generates back into the conduits, overloading them. Each conduit requires multiple hits. Combine Soldiers will constantly attack you, so prioritize them with your Gravity Gun or other weapons. Alyx will help by targeting Breen's shield and providing cover. Once all conduits are overloaded, the reactor will destabilize, leading to a massive explosion. The G-Man will appear to extract you just before the Citadel's destruction, ending the game on a cliffhanger.