The final boss in Half-Life 2 is Dr. Breen, but to defeat him isn't about a traditional boss fight like you would expect. Instead, it's a series of tasks and puzzle-solving moments that move the story forward. Here's a step-by-step guide on how to 'defeat' Dr. Breen: 1. Firstly, always make sure your health and suit are fully charged. There are charging stations within the reactor room where you can regularly top up. 2. After a cut-scene, Dr. Breen will start attacking you with Combine soldiers and a bouncing energy ball. Keep moving to evade these attacks. Use the gravity gun to fend off the soldiers as you progress upwards. 3. You need to ascend the reactor structure, while the area is under heavy guard. There are several lifts that help you do this. Always be on the move, and take cover whenever possible to avoid the energy-ball attacks. 4. Once you've cleared the area of enemies, look for a large red button near the force-field and press it. This will cause a reactor core to briefly open. Shoot this core with the gravity gun. This leads to a weak point being exposed in the reactor. 5. Your final task, once you've made it to the very top level and pushed the final big red button, is to fire at the reactor core with your gravity gun three times (it will get increasingly harder as there will be more soldiers attacking). 6. After landing the third shot, an end-game cut-scene starts playing and congrats, you have 'defeated' the final boss! Remember: it's all about staying focused, keeping on the move, maintaining your health and suit charge, and slowly but surely ascending to the top to take the final shots at the reactor core. It might take a couple of tries, so don't get disheartened – keep at it, and you will succeed! Enjoy the end of an iconic game.