Can you think of situations in wuxia wherein a good/heroic character needed to (and successfully carried out) the killing of a loved one/friend/student for the good of the world? For some reason, the former loved one/friend/student turned evil, and much to the good character's regret, he/she had to kill the traitor for the good of the world and/or justice.
The only example I could think of is Cheung 3 Fung's execution of Sung Ching Sheu at the end of HSDS (and, if it's novel canon and not a TVB innovation, the similar execution of Cheun Jen Sect third generation member Chiu Tze Ging by his teacher, Wong Chui 1). Are there any others?