If there is room on the item to imbue you could imbue luck on it to remove the negative.
I don't think -100 luck is that bad at all if its a good artifact. Can you post up the other mods on the item? If it has a high intensity then there might not be room to imbue the luck.
I consider -100 luck the "best" negative mod you can get on an item. Cannot be repaired, brittle or cursed are far worse!