Take your pick. None. Wait, maybe I should say Yan Hung just because she wasn't as 'evil.' Then again, it is easier to make a villain more evil in ancient and premodern series. Oh, whatever. Both characters are perfectly hate able.
Lee Sing Cheung's "Au Yeung Cheung" vs. Susanna Kwan's "Chung Siu Sa"
Both get excited at the sight of money. It's that simple. They're greedy and selfish. However, Ah Cheung is just a background character to make the Koo household a bit more noiser and fun. While Chung Siu Sa proved to be incredibly annoying at times, she was one of the main characters who was greatly developed.
Take your pick. Chung Siu Sa of course. Yes, she was annoying at times, but I loved the change she underwent. She had multiple layers and you could sympathize with the character. Of course, the character wouldn't be nearly as entertaining and easy to love if it weren't for the talented Susanna.
Nancy Wu's "Chow Bing Bing" vs. Kate Tsui's "Lo Ka Mei"
Chow Bing Bing is practically a complete copy of Lo Ka Mei. They both give off the impression that they are 'sweet and innocent' when they are truthfully conniving with a heart full of...envy? They have a past of messy relationships. One is an adulteress and gold digger while the other became pregnant as a teen and cruelly put her son into an orphanage (and may I add was so stupid as to get pregnant accidentally again with the same guy). As they both fall for a man, they quickly realize that the man's non blood related sister is in love with them. Even though both women don't do anything to pursue the relationship further, Chow Bing Bing and Lo Ka Mei were keen on ruining their love rival's lives.
Take your pick. Chow Bing Bing. Don't get the wrong idea, I hate both. Chow Bing Bing barely made an impact on the overall plot and merely served the purpose of coming between Koo Yu Cheung and Ah Ngan. Ka Mei however makes Moonlight Resonance go downhill with plenty of screen time and ridiculous schemes. Also, Nancy is a much better actress than Kate.
It's amusing how despite all the similarities between the characters of A Fistful of Stances have to Moonlight Resonance, I liked all the characters of Fistful more (except Au Yeung Cheung vs. Chung Siu Sa). Hey, A Fistful of Stances may have borrowed quite a bit from Moonlight Resonance, but at least they made it better!