I've never really thought about it before, but now that I have, I don't really understand exactly why Yeung Teet Sum decided to commit suicide in LEGEND OF THE CONDOR HEROES. At the moment that he chose to kill himself, he had essentially *won* his struggle against Yeun Nan Hung Lit. Yeung Teet Sum had reunited with his wife, Pau Sik Yerk, and her love was for him alone, not Yeun Nan Hung Lit (and not all of Yeun Nan Hung Lit's wealth, power, and retinue of martial artist flunkies could change that). The only thing Yeung Teet Sum lost was his son, Yeung Hong, who had chosen to throw in with his adoptive father, but Yeung Teet Sum had already accepted that.
It was a completely unexpected decision, and in retrospect, an inexplicable one.