'Plantera, the Destroyer'. Well the Destroyer can't fly, so if you make a box very high up. but not to high so they don't despawn, you could just defeat them without needing anything else other damage output and ammo or mana or just time.
Terraria Community Forums
Animus Viral
Techhunter_Talon
The Stormbow (dropped by Hallowed Mimics) with Hallowed Arrows is deadly to the Destroyer.