Vilethorn

The thorn erupts from where you are standing and grows outward, ignoring terrain completely. That is the whole reason to carry it. You can sit behind a block wall and delete whatever is on the other side, and nothing else this early in a run lets you do that.

Everything caught inside the thorn takes several hits as it extends, and it never stops at the first target. Worms eat the full length of it at once, which is why the Eater of Worlds folds so fast. The Creeper phase of the Brain of Cthulhu is the same story. Against one compact enemy the damage is unremarkable and you should be swinging something else.

Mana cost is low enough that a stationary player with a decent pool can fire continuously and never run dry, so it doubles as the weapon you use while regenerating. The small knockback on each tick also pins weak enemies in place, which turns a corridor full of zombies into a non-event. On desktop the Ruthless prefix edges out Mythical here, a quirk of how such a small damage number rounds.