Terra Blade

The visible blade is the smaller half of the attack. A green field trails the arc, reaches past the tip, and covers ground behind you on the backswing, catching a few bodies at once. Every swing also throws a fast slash that keeps traveling through whatever it touches until it clips a wall or runs out of steam.

Each enemy the slash passes through takes a bite out of what is left of it, so by the fourth or fifth body it is barely doing anything. Against a packed corridor that is fine, because you are hitting the whole line at once. Against a boss with an escort it means most of your projectile output disappears into the adds. Standing at range and letting the slash do the work is comfortable, and it is also the low damage option: the full number needs the swing and the slash landing on the same target.

The slash comes out once per swing rather than on a timer of its own, so anything that speeds up your attack speeds up the projectile stream with it. The catch is that this sword only takes part of any melee speed bonus, so a stack of speed buffs does less here than it would on another broadsword. Still worth building for, just not worth chasing past raw damage. Legendary is the reforge.

Knockback always pushes enemies away from you regardless of which direction you swung, so a panicked backswing buys you space instead of dragging something closer. The blade, the aura, the slash, and the sparks they leave behind are all fully lit, which makes an unlit cave readable while you are fighting in it.

Eight separate swords go into it before you are finished, most of which you would pick up on a normal run anyway. Treat it as a background project from the moment you enter Hardmode rather than a shopping list you start after Plantera, or you will spend an evening waiting on a Solar Eclipse for a Broken Hero Sword. What you end up with is the piercing beam of the True Night's Edge bolted onto the wide swing of the True Excalibur, still shaped like the Night's Edge it descends from. None of the effort is wasted later, since the finished sword feeds straight into Zenith.