User blog comment:SilverHexxitFights/Which is Terraria's Hardest Boss?/@comment-24167312-20131115235351

The boss list greatly depends on the current situation you encounter them, and the gear you have. Plantera is the easiest boss with Vampire Knives, or a self-healing item, however same for some other bosses. Skeletron Prime still poses some sort of threat even with very high end game gear. Pumpking is a weaker Skeletron Prime, however they quickly swarm and do extremely high damage when swarming. Mourning Wood simply requires a little skill to dodge its projectiles.