The Destroyer/Strategies

These strategies will work with any character, but high accuracy or bullet regeneration is recommended for the second:

If at this point in the game you have any Eridian weapons, equip them and use either them or an assault rifle to take down three of the four purple tentacles (leave one to stop the rest respawning.) Now just fire away while hiding behind the stone pillars for the duration of the eye attack; this should allow you to kill The Destroyer with ease and without you having to worry about ammo. An extremely effective weapon is the Eridian Thunderstorm. While it recharges, just use another weapon to take the purple tentacles down.

Make certain you destroy the purple tentacles whenever they appear. Stand behind one of the large rocks that has a half circle removed from one side. Through this, if you are careful, you can have shooting access to the eye. You will only have to worry about the slam, as the beam will not be able to penetrate the rock, and The Destroyer is unable to aim for anything but the center of your body; which is behind a rock. You will be safe, and have an easy avenue to The Destroyer.

An extremely effective weapon against The Destroyer is The Boom Stick, especially if you have a increased clip size via class mods or skill tree. It's fast fire rate, high damage, make it extremely effective. It's spread is also somewhat negligible against this huge target.

Another strategy is to move to the left side of The Destroyer itself, this will prevent it from attacking your character, making it very easy to kill if you have a means of ammunition regeneration.

It has also been reported that running up and throwing multiple MIRV grenades into the destroyers mouth can result in an easy kill. This can also be done with a fast-firing rocket launcher or shotgun-rocket-launcher.

In addition, using a scope to aim a Longbow grenade into the destroyers eye will result in the grenade critically hitting the destroyer, with 7 grenades being able to take roughly a quarter of its life.

Hunter

 * If you wish to be a sniper, get yourself a sniper rifle, get a sniper rifle ammo regeneration mod (for when you run out and there is an extremely high chance you will).
 * Once the battle starts head to either left or right (it doesn't matter just get in the general area of one of the 4 main pillars near the boss).
 * Take out three of the purple tentacles that throw the explosive spines.
 * Leave the fourth one, if you somehow after destroying three of them manage to get taken down you can use the 4th one for your second wind. Don't destroy that fourth one throughout the battle (as long as the last one doesn't die the rest won't respawn.)
 * Once you've destroyed the three of the purple tentacles you can spend the rest of the fight concentrating on the eye. With 5 points in CALIBER, DEADLY, and mod that either increases critical damage, or sniper rifle damage (like a +caliber sniper mod/+deadly gunslinger mod).
 * With five levels of Lethal Strike the hunter will do 233 damage, or 5000 damage for a critical hit. This can be used after the Destroyer wraps its tentacle around the first rows of pillars.
 * This battle will progress REALLY quickly (in the area of about 2 minutes) if you have the Jakobs Skullmasher sniper rifle, they do in excess (with applicable mods/skills) of 15,000 per critical hit.
 * Also, if you stand back near the New-U station, you can unload a assault rifle (or anything else that has a decent accuracy) into The Destroyer's mouth. I did this using an assault rifle with a damage of 100, and it took about 300 or 400 bullets, but it works.
 * If you wish to do it as a gunslinger, an ammo regeneration mod is again recommended.
 * If you have a large clipped repeater and a high rate of fire, you don't need to worry about getting criticals, just fire away from behind the pillar until he is dead.
 * As most high fire rate and large clip repeaters are not particularly accurate anyway, focusing on the critical locations can leave you vulnerable. Instead, just aim in the general direction.
 * It can be killed with about 800 pre-modified shots from a ~60 damage repeater. It will take many more if you don't have Gun Crazy and Hair Trigger. Critical hits happen regularly enough from scattered shots.
 * Your Bloodwing will hit the Destroyer's mouth if you are close enough. Explosive is the only element that is effective.

Soldier

 * For an assault rifle gunner, equip ammo regeneration of any kind, be it a gun, a class mod, or skill. Take cover and fire, throwing a Scorpio Turret whenever it's ready.
 * For a Shotgunner, move into close range if you have a soldier medic on your team.
 * Overload is a useful skill to bring to this battle.