Still Hungry

The point of no return for your world's innocence. Summon the Wall of Flesh by tossing a Guide Voodoo Doll (Voodoo Demon drop) into Underworld lava - apologise to the Guide - then outrun a screen-wide wall while shooting it. Build a long Underworld bridge first (a few hundred blocks of platforms/ash), bring a piercing weapon for the Hungry, and a Hellfire-arrow bow or the Bee's Knees does the damage. Victory drops a Pwnhammer and flips the world to hardmode (It's Hard!) - there's no going back, but nothing is lost either.