The Final Combat (1989)

Koo Fung's twin brother Koo Yim Yeung (Ng Man Tat) had turned evil after practising a martial art called "Yuk Liu Sun Gong" that will make a man turn woman-like. All the good clans conspire to destroy this major evil sect which is headed by Koo Yim Yeung. Koo Fung's teacher (Kwan Hoi San) has decided to learn a martial art, in order to fend against Koo Yim Yeung, that will make the person very powerful, but will cause the person to die very soon after. Koo Fung is adamantly against his master sacrificing himself and plotted with his martial brother, Duen Hoi, to steal the kung-fu manual so that he can learn it instead and kill his twin brother. However, during the attempt, Duen Hoi accidentally kills a fellow martial brother and in trying to hide his own blunder, Duen Hoi accuses Koo Fung of the murder. Koo Fung is chased down a mountain cliff by his clan and believed to have died. Duen Hoi, in his guilt, confesses under pressure to his master and took in Koo Fung's infant son, Koo Yuk Lau (Francis Ng), to raise as his own. Duen Fei (Stephen Chow), his real son, grows up to be a business-wise person but has no interests whatsoever in learning martial arts. He gets into a lot of trouble hanging around in the streets and is admonished by his father all the time. Koo Yuk Lau, on the other hand, is like a male prodigy--great wit, great martial arts, and leadership potential all in a package. Trouble begins to stir of course when he finds out who his real father is and when Koo Yim Yeung returns to cause more ruckus