Boulder Lord

Defeat the Moon Lord on a For the Worthy world (or getfixedboi, which layers it in) - there his forehead eye lobs enormous boulders on top of the usual deathray-and-eyes routine, and everything hits harder. Come with post-Moon-Lord gear from a normal world if you want mercy, or take the FTW fight straight for the full experience. The kill pops it; see Champion of Terraria for the base tactics.