As evident by the unlimited items glitch using the W-Item Materia in “Final Fantasy VII”, there are certain bugs and glitches with the game that could potentially be exploited if done correctly. One such glitch is the Overflow damage bug.
While it is most easily done with either Vincent or Barret, most any character in the game is able to exploit the Overflow glitch. Using Vincent as an example, the glitch works like this. Vincent's ultimate weapon, Death Penalty, deals more damage for each enemy that Vincent has killed. While damage caps out at 9,999, the power of Death Penalty will keep growing with every kill.
As a result, if Vincent's kill count became high enough, with the maximum number of kills be 65, 535, then Overflow occurs and instantly kills the enemy attacked. While this mechanic works differently for other characters, as their weapons do not have the same special ability, the ultimate goal is the same.
Another way to trigger the Overflow is with Barret and his ultimate weapon, Missing Core. This ultimate weapon powers up with the AP from Materia equipped to it. Meaning, if enough MASTERED Materia is equipped to the weapon, the amount of AP would be so great that Overflow would be possible.
For the rest of the characters, Overflow can be achieved via Limit Breaks or even regular attacks, if paired with enough Hero Drinks and Berserk, both of which greatly raise attack power. It is an extremely useful glitch if one does not wish to have a challenge when facing certain enemies such as Ruby or Emerald Weapon and simply wish to claim their rewards.