use explosives. and anything that can pierce multiple enemies. and an arena that goes quite high. Campfires, heart lanterns, sunflowers, grindstone, bewitching table, an ORB to ponder that can be bought from the wizard perhaps? don't forget a few potions too.
If this isn't enough please refer too the wiki for future reference.
check out community forums. destroyer isnt hard at all. stay above on high heights keep away from your huse. When you get to low hp teleport back to you house for nurse healing. destroyer will not despawn.