In LEGEND OF THE CONDOR HEROES, Iron Palm Union Chief Kau Cheen Yan killed his enemies because he was an ambitious wulin figure who wanted to win the Mt. Hua Sword Tournament so that he would be known as the world's best fighter, and so that his Iron Palm Union would be known as the most powerful force in wulin. Naturally, then, he needed to kill people who got in his way. He did not, however, have some kind of psychosomatic addiction to killing that caused him to suffer severe physical/mental anguish from *not* killing.
As the monk Chi Yan in RETURN OF THE CONDOR HEROES, however, Kau Cheen Yan seemed to have some psychosomatic addiction to killing. He was *literally* in pain because he did not allow himself to kill. What happened? Nothing in LOCH ever suggested that he was addicted to killing...only that killing was a necessary deed for him to achieve his goals.