Starlight

The sword itself passes through enemies without doing anything. Every point of damage comes from the burst of light it throws forward on each swing, which is why it plays less like a rapier and more like a very short flamethrower. Those beams stop dead at solid ground, so anything on the far side of a wall is safe unless it can phase through the wall itself.

You have to be almost touching the target. That makes the Titan Glove line and any size prefix worth far more here than on a normal sword, since both stretch how far the beams carry. Swing speed prefixes are wasted: the attack rate is fixed and melee speed bonuses do nothing to it.

Anything big and slow that you can stand next to. The beams pierce without limit and land many times a second, so a Golem or a packed lane of event enemies evaporates. Fast fliers that never sit still are a different story, and the damage number on the page will flatter it badly in those fights. The Solar Eruption reaches much further; this trades that reach for hits that connect every time.