Corruptor

This is the grown up version of the Eater of Souls, and it appears in the Corruption the moment your world converts. Early Hardmode is exactly when it does the most damage, because it arrives while you are still wearing what got you through the mechanical gate. Do not treat it as a bigger copy of the thing you were swatting an hour ago.

Given a clear line to you it lobs a glob of vile spit every few seconds. Two properties decide the fight. Any hit from anything pops the projectile in the air, so you can shoot it down instead of dodging it, and it cannot travel through tiles, so one row of blocks between you and the enemy switches its ranged attack off completely. In exchange it hits much harder on contact than the other destructible projectiles in the game, and the Weak debuff it leaves drags on your output for the rest of the trip.

Its firing timer resets every time you land a hit. A weapon with any real rate of fire stops one from ever getting a shot away, which is why a slow heavy swing feels worse here than a fast weak one. If you are building rather than fighting, a knockback minion like the Spider Staff pins them off the work site and keeps resetting that timer for you.

Vile spit can be bounced on. With the Slimy Saddle or the Gelatinous Pillion you land on the projectile instead of eating it, which makes anything arriving from below harmless. The queen slime mount is much better for this than the king slime one, since the wings give you the height and the control to line the bounces up on purpose rather than by accident.

The spit used to spread corruption where it landed, which is where the name came from. That behavior was cut a long time ago and the name stayed. The similarly named Scourge of the Corruptor has no connection to this enemy at all: the weapon does not come off one and gets no bonus against one. It also trails an afterimage as it drifts, the same effect the Twins leave behind them.