Unnatural Born Killer

In the Ming Dynasty, Lord Yim Sai Fan kept professional assassins to get rid of those against him. As he considered Lord Yeung Kai Sing a thorn in his flesh, he sent his “Twelve Animals Killers” to wipe out the entire Yeung family. However, since the Yeungs were good fighters, the “Twelve Animals Killers” failed to accomplish their mission. Fan, therefore, sent his last card, the “Man Killer”. The “Man Killer” had to complete the task before the night ended since he would regain his conscience in the day.
When the “Man Killer” reached the Yeungs family, their finest fighter Ching, who was Sing‘s son, was incidentally called away to attend a meeting; thus the whole family were slaughtered. However, just as the “Man Killer” killed Sing’s daughter-in-law, dawn broke. He was shocked by his own cruelty and was terribly ashamed. He decided to turn against Fan. Fan, therefore, had to exterminate him.
(Source: tvbanywhere)