What weapons to use to kill the Destroyer?

One of the easiest methods of killing the Destroyer is to use the Daedalus Stormbow. This item has a 20% chance to drop from Hallowed Mimics. Hallowed mimics can naturally spawn in the underground Hallow and in Hardmode worlds you can also use 15 Soul of Light to make a Key of Light and put the key in an empty chest which will cause it to become a mimic:

Hallowed, Corrupt, and Crimson Mimics can also be summoned manually by the player, in Hardmode worlds only, by placing a Key of Light or a Key of Night inside an otherwise empty Chest; the Chest becomes a Mimic once it is closed

The reason this weapon is so strong against the Destroyer is because it has a high rate of fire and also produces several projectiles for the cost of one ammo. Because the Destroyer is so long, it's nearly impossible to miss unless it's underground. The best ammo to use with the Stormbow is Holy Arrows, since each hit will spawn additional star projectiles for added damage.

As for strategy, I usually set up a very simple arena shaped like a flat U. I make sure it's floating about 50-100 blocks above the ground.

*          *        * = Solid block
*          *        C = Campfire
*          *        H = Heart Lantern
*    C     *
************        (Actual width should probably be around 30 blocks)
     H

This shape prevents lasers from the main body from hitting you, which makes you effectively immune to the Destroyer itself (unless it approaches at an almost vertical angle and manages to jump straight up to the arena, which shouldn't happen often). The only thing you have to worry about are the drones - since they can travel through blocks and often end up above you, they will start shooting down towards you. This is why the arena should not have a ceiling - you can use the Stormbow to clear out those pesky drones.

Using this setup, with the right ammo and potions/buffs, possibly combined with other suggestions here (Nimbus Rod helps a ton as well), it's pretty trivial to kill the Destroyer in 30 seconds to a minute without much risk to yourself.

I found it it pretty hard to do the destroyer with melee equipment (and that was with adamantium armor).

I think you will need the extra durability that is provided by hard mode armor to take down the destroyer, but if you are stuck with pre-hardmode equipment you will probably want to use a setup that has a decent amount of DPS and focus on dodging attacks.

• Weapons: Either Clockwork Assault Rifle (Wall of Flesh drop) and party bullets or Minishark with Meteor Bullets.
  • The former has more damage, but the latter is easier to get and can hit twice with each bullet, which is really useful against the destroyer.
• Armor: Necro Armor will give the best ranged DPS.
• Accessories:
  • Ranger Emblem
  • Cross Necklace
  • Leaf Wings (You can buy these from the witch Doctor as soon as you get into hard mode)
  • Charm of Myths
  • Obsidian Shield

If you can get the avenger emblem and the ranger emblem, that would be ideal. I expect that you will want to have these all forged to be warding so that you can survive, but you might try them with Lucky or Menacing to increase your DPS even more. It really depends on how good you are at dodging.

You will want to use potions during the battle as well. Endurance, Iron Skin, Wrath or Rage, and anything that gives the Well Fed buff will be very useful.

I think you will have to be very good to do this without hardmode armors, though.

I'm a little late to the party, but with a Battle Potion and a Water Candle in the rain, you can farm up Nimbus Rods very quickly. The Nimbus Rod DESTROYS the Destroyer. It does so much damage that I went from having a rough time attempting it with other weapons (Sunfury) to buffing myself and oneshotting it. If you have enough defensive stats and regeneration and a Nimbus Rod you can kill it in less than a minute.

The Destroyer was relatively easy for me to beat. Let me share my method.

You want to have a good sword with good DPS, such as the excalibur, fiery greatsword, or a titanum sword. Go to hell, and mine some hellstone. (You can use meteorite as well, but I wouldn't advise this because it causes meteor heads to spawn)

Make a long line of selected material floating in the air or on the ground, and get a cross necklace. If you are wearing an obsidian skull, remove it. Make sure you have a shield of some sort to protect you from knockback. (Make sure it's not an obsidian shield because this will protect you from fire damage!)

When you take fire damage, it only deals one hp of damage if you have good armor. When you have a high amount of health, this will not matter. When you take damage, it'll give you immunity, making it far more difficult for the destroyer to attack you.

Make sure you have a good bow of sorts, I'd prefer one that does damage after the initial shot is fired, (like the sharanga) And make sure you always drink your potions.

Unlike John Clever's answer, I prefer to do it with melee equipment. It's a lot easier if you first get at least Mythril/Orichalcum armor and a Titanium or Adamantite sword. Set up as many heart statues as you can find (within a reasonable amount of time of course) and wire them up to 1-second timers.

I've never been able to kill the Destroyer in Molten Armor. If you're good at dodging, I recommend Menacing on all accessories. If you aren't, then go for Warding.

The good thing about the Destroyer is that he's REALLY long, which means you can camp beside him while he's digging around and rack up high damage.

Accessories... You'll probably want a Cross Necklace, maybe a Star Cloak as well (you can combine these to get a Star Veil, so you can save a slot). I'd leave off the Cobalt/Obsidian Shield and go for Charm of Myths, Warrior Emblem, Wings, and Frostspark Boots, if you have them. Lightning Boots work as well.

I say to leave off the shield because then you will be more aware of when you're being hit. And potions couldn't hurt. Lots of potions. All those defense/damage/critical strike buffs.

The following is taken from an edit to the question

We've tested a new technique yesterday with considerable success!

We used stacks of Grenades, along with a very very long skybridge about 100/150 above surface. In the middle of the skybridge, we've setup 3 levels high (about 50 in between). Camp fires spread accross.

Gear-wise, we have Molten gear, each a Obsidian shield, Harpy / Demon wings and a magic mirror. The strategy is to drop grenades at the worm, when our HP get's too low we rurn away from the spawn then teleport. Our spawn is setup next to the nurse. Heal up with her and return to fight.

This takes about 5-6 minutes, after which we gain access to Megashark + Explosive shot which unlocks the rest of the speed run.

If memory serves, I used golden shower and adamantite armour the first time I killed the destroyer, Though I hear flails are very effective too.

One of the most efficient, albeit cheap, methods that I've found that allows a Destroyer kill so soon into Hard Mode would be the use of the Cannon. To get the cannon, you'll have to follow a series of steps:

1. Kill enemies in the ocean biome until you get a Pirate Map (1/100 chance).
2. Summon the Pirate Invasion and defeat it to unlock the pirate NPC. This may also yield some nice beginning-HM loot for you (Cutlass, Pirate Staff).
3. Purchase a cannon from the pirate NPC for 25 gold.

Once you've got a cannon, place it high enough to where the Destroyer cannot attempt to collide with your character (the video here shows 400'+) and simply rain cannon balls on the Destroyer until you've defeated him. I would suggest getting creative with walls to stop the orbiting eyebots from using their lasers on you.

Additionally, I would suggest placing a campfire, heart lantern, and a pool of honey nearby as well as using a Regeneration Potion (if you've got one) to prolong your life as much as possible.

A strategy I would use is a high tower of wood platforms, high enough so the destroyer barely gets to you, and when the destroyer does get to you, it will have gone so high it will have a super slow velocity, giving you plenty of time to dodge, and then you can do some crazy DPS by using a melee weapon.

I'd recommend a Daedalus stormbow, but on mobile use the sharanga to get spectral arrows and use a adamantite/titanium repeater. Use full 2nd hard mode armor(Mithryll/Orichalcum), and stay where he can't get you.

Try reforging items... And if you are on console/mobile, get a sharanga. It cans do 35 damage, and turns any arrow into ocram's dropped arrows. For mobile, you can make backup characters and duplicate with a chest for coins. I got 1345 platinum ?