Shoot it Until it Dies (Cyberdemon Boss Battle) - DOOM

Defeat the Cyberdemon - 25

You will encounter the Cyberdemon at the end of Mission 9 - Lazarus Labs.

You will arrive at the giant doors, which you'll open, then be dragged through by the Cyberdemon.

It has a large barrage of attacks:

Rocket Barrage

Rush

Melee

Laser Cannon

Rocket Barrage - The Cyberdemon will do one of two things, shoot at your with around 10 rockets from a rocket launcher, or he will shoot upwards, and make most of the floor to be covered by laser-guided rocket markers. You can avoid the Rockets by sidestepping, while you just have to not stand on a Guided-Rocket Marker.

Rush - The Cyberdemon will rocket propel itself towards, attempting to slam against you. You can easily avoid the Rush attack by sidestepping away.

Melee - The Cyberdemon will swing at you with it's strong muscular arms, he will only use this attack when he is close to you. If you are a fair distance away from it, he won't attempt to Melee.

Laser Cannon - The Cyberdemon will use he's Laser Cannon, you'll know when this is happening because it will begin a laser pointer, then suddenly discharge and emit a large powerful laser. This can be avoided by jumping and sidestepping away from the laser pointer stage of the attack.

Once you weaken the Cyberdemon and remove it's cyber-heart, the cyber-heart will explode and send you and the Cyberdemon to a more demonic version of the battlefield.

Now the Cyberdemon is faster and more agile. He's attack now include:

Rocket Barrage

Rush

Melee

Laser Cannon

Hell Wave

Demonic Sword

Hell Wave - The Cyberdemon will spawn a hallway of spikes, forcing you into a tight corridor. While in this hellish corridor, the Cyberdemon will doe one of two things. Shoot a barrage of rockets at you, or use he's Demonic Sword. You can avoid the barrage of rockets by jumping and sidestepping, while the Demonic Sword will emit 3 Hell Waves; you can avoid them by jumping the first, standing for the second and jumping for the third.

Demonic Sword - The Cyberdemon's Demonic Sword emits Hell Wave which you can avoid by jumping and standing to avoid getting hit by the Hell Waves. He will also use the Demonic Sword at close range which does double the damage of his normal Melee Attack.

Once you have defeated the Cyberdemon, you will be transported to another location in Hell.

I found that the Heavy Assault Rifle, Plasma Rifle & Rocket Launcher worked the best in the first stage, while the Rocket Launcher, Plasma Rifle, BFG & Chaingun worked best in his second stage.

Cyberdemon