This is a very quick guide on how to beat the destroyer. He is the first hardmode boss you should face.
The Arena and Buffs
The arena can be basic and made of wooden platforms with a couple of campfires and a nurse nearby if you are near death. You can also add whatever decorations or stuff that you like.
You should use the wrath potion, any food that gives you the Well Fed buff, ironskin potion, regeneration potion, heartreach potion and any other potions you think will help you. You can use more potions but these are the basics.
Recomended Weapons and Equipment
You can use any early hardmode armor you want, but if you still can't beat him use Adamantite or Titanium armor.
Night's Edge, Dao of Pow, Shadowflame Knife, Ice Sickle, Cutlass, Fetid Baghnakhs, Amarok, Hel-Fire.
Medusa head(It's has only 1% chance to drop from medusa), Nimbus Rod(Also a bit rare), Meteor staff, Golden Shower, Shadowflame Hex Doll, Crystal Storm, Crystal serpent(Rare).
Daedalus Stormbow, Adamantite/Titanium Repeater, Onyx Blaster, Dart Pistol/Dart Rifle, Star Cannon, Gatligator, Uzi.
If you still have trouble use Nimbus Rod and Daedalus Stormbow at the same time. This will deal massive amounts of damage and even a potato should be able to beat him then.
Obsidian Shield, Star Veil, Any Wings, Charm of Myths.
Good Luck Fighting Him
Just try to dodge his attacks and attack him as much. Try to avoid his HEAD because that hurts a lot. Don't forget to drink your potions and try to learn his attack pattern. Basically just try and try he isn't that hard.
Written by SimonaS.