Yin 13 is known as one of the deadliest swordsmen in the Gu Long canon - perhaps even the deadliest?
But by the standards that measure the skill of wulin swordsmen, could he really be considered (what PJ would call) the "peak of perfection" in swordsmanship? The whole thing about him is that his 15th stroke could not be pulled back. Isn't it said somewhere that a swordsman cannot truly be said to have reached the pinnacles of swordsmanship until he has mastered the art of pulling back, at will, any stroke he has stricken?
Yin 13 could not do this.