Imma just copy and paste
In chapter 296, it’s revealed that the Z-Gun[12] is the first weapon you receive once you pick Option 2 from the 100 point menu. In chapter 247, the weapon is shown in use for the first time. It seems to apply severe gravitational force in a circular area and force everything within range of the shot to slam into the ground or be flattened, even a few inches of the floor below the shot is cut out. Some powerful enemies have been shown to survive multiple blasts with this weapon. Exceptionally strong enemies have been shown to partially resist the gravity effect with sheer, brute strength — reading the manga closely, it can be noticed that this happens because the weapon must be charged: if you press the trigger for a long time, the “gravity smash” will be stronger. If you repeatedly shoot it without charging, the “gravity smash” is weak. The Z-Gun doesn’t appear to have a time-lag.