I made this for my little 5e campaign and heck it works for OSR games too. And the basics work with any weapon. Not just glaives and polearms but that’s what the fighter was using. Originally, the weapon was a trident but I changed it at the last minute. Here’s the low down.
Roll damage twice. Take the higher number and apply any modifiers that you happen to use in rules set of choice. The target takes that damage. The wielder takes damage equal to the lower roll. If you happen to using the latest rules where damage the type of damage is important, I made it psychic damage. The weapon slows erodes the wielder’s pysche.
There you go. A quick little double edged sword so to speak.