Instructions
How to Beat Drek in Ratchet and Clank
Check your inventory to make sure you have the following weapons: RYNO, Devastator, Visibomb Gun and the Blaster. If you are missing any, check the Gadgetron store to purchase them, and fill up on ammo.
Set your quick select with the weapons listed above as well as the Gadgetron PDA and Swingshot. The PDA will allow you to purchase additional ammo during the battle and the Swingshot will prevent you from falling to your death should Ratchet accidentally jump off the platform.
Use Clank's punch attack and atomic blast to knock the first section of health away from Drek. You begin the battle as Clank, so just run up to Drek and mash the attack button--he is a pushover at this stage of the battle.
Move in a circle around Drek, jumping over his Fire Waves while avoiding the Random Missiles. The missiles will mark the spot on the platform they're going to hit, so if you keep Ratchet moving, he won't be affected by their blasts.
Use the RYNO or Blaster to fire at Drek after successfully dodging a Fire Wave attack. The RYNO will make short work of Drek, while the Blaster will eat away at his health and still allow Ratchet to move and jump around the platform.
Follow Drek as he leaves the platform and lands on a new one. Ratchet will have to jump across several broken platforms and use the SwingShot to reach Drek's new location.
Defeat the mines that Drek sends after you by using your wrench. Keep your focus on Drek and attack with the Devastator after a successful Fire Wave dodge. Be careful not to get hit by mines during your attack.
Work your way to the third platform after Drek leaves the second platform behind. You'll jump across falling platforms, so make sure to use your SwingShot and glide ability during this section. Once you reach the final platform, move to the lock in the center of it.
Continue your attack using the RYNO or Devastator until the countdown clock reaches ten seconds. Then, jump and slam Ratchet down onto the lock. This will cause Drek to begin using a heat ray.
Dodge the heat ray by leaping backwards with Ratchet while continuing to attack Drek. He will send out drones that can be taken care of with the Blaster. Any time he begins the countdown clock, slam down on the lock to stop it. Repeat this pattern until Drek has been defeated.