One hit kill moves in a game with PK was BS, but undead armor is even more BS.
PK where there's no detriments for the PKer, but tons of detriments for the people killed was ridiculous and there needed to be a solution for the fact that PKers got a OHKO. However this solution is pretty stupid as well since it forces people playing the game to only use one type of armor. Plus the fact that the the armor is only obtainable in a quest that has very specific requirements means that the economy for that games would quickly get fucked. Guilds that can complete the quest would corner the market on the armor and everyone who wants to play the game without dying in one hit would need to either join the guilds in question or have enough money to buy the armor from those guilds. It's a bad solution for a skill that shouldn't even exist in a PvP game.