Malice

Malice, made from Ith + El + Eth, in that order. This works in all melee weapons. Possible in v1.08 and above.

These are all relatively common Runes, so if you can find them and a three-socket melee weapon, you are in business. The added damage isn't that big, just +33%, but the other mods are pretty nice. The -100 defense is cumulative, and is a monster flag, so anything you hit with it will be lower defense to everyone in your party, not just you, and the more you hit monsters the easier they'll become to hit again. This would probably be best on a fast attack weapon for a character who had a lot in Crushing Blow, or possibly if you were looking to convert the monster, rather than kill it.

 Weapons Runewords