"of punishment" suffix or "punishing" prefix
Props to (Borror?) for suggesting in another thread that additional damage could be added for every point that a to-hit roll exceeded the defender's AC. Not sure if this was for a particular class or type of attack (eg Power attack) or just to be applied in general, but I thought the idea was great. Assuming they didn't implement that, I would propose the following:
"of punishment" or "punishing"
If the combined attack roll (including all bonuses) is 10 points or more above the defender's AC, then this weapon does an additional 3d6 damage. Or perhaps 1d6 damage for every 5 points above AC the to-hit roll achieves (to maximum ???). (In other words, the weapon punishes you for having poor defense.)
Example. +5 holy burst longsword of punishment or +5 punishing longsword of pure good
Note: I'm not at all familiar with PnP sourcebooks. In the event that this suffix/prefix name already exists, another name could easily be given.