Slayer of Worlds

Every boss in the game downed - the full ladder: King Slime, Eye of Cthulhu, the evil-biome pair (both Worm Fodder and Mastermind, so a second world or opposite-evil farm), Queen Bee, Skeletron, Deerclops, Wall of Flesh, Queen Slime, the three mechs, Plantera, Golem, Duke Fishron, Empress of Light, Lunatic Cultist and the Moon Lord (Champion of Terraria). Both world evils is the only bit that needs planning; everything else is the natural completionist road.