I've been pondering over XAJH and several interesting things popped into my mind.
DFBB undoubtedly was wicked ambitious during the events 12 years before the start of the novel. He tirelessly schemed to usurp Ren Woxing's position and finally succeeded. Then, his ambition grew and he decided to study KFBD to further his skills in his attempts to take over all of wulin.
Fast forward to the start of the novel. DFBB after having trained in KFBD is widely recognized as the #1 fighter in the entire martial arts world. LHC early on even admitted to this to TBG as they were dueling in the tavern. DFBB's skills were so widely accepted as #1 that even a disciple of Huashan knew about it.
Anyway, the ironic thing here is that DFBB's ambition during all those years have pretty much dissipated, like his manhood. All the matters of the sect were handled by Yang Lianting and DFBB's daily routine consisted of sitting, sewing, and seducing his Big Brother Yang. Was this a normal side effect of KFBD? That the user would become so effeminate and lose all ambitions and goals? I remember DFBB saying how all he ever cared for now was to become beautiful and so on and the matters of wulin, becoming emperor, etc that had once captivated him he could care less about now. This is quite a stereotype about the ambitions of women from Jin Yong.
How ironic that learning the #1 martial arts in the world causes one to lose all worldly ambitions. Anyway, another thought popped into mind. LHC had witnessed the effects KFBD had on its practitioners. He should have just let YBQ and LPZ go about their ways since eventually they would just settle down, throw their ambitions out the window and become subservient little housewives.