Spoiler warning for every drama I will mention, it will be related to the OP's requirement though.
Okay the shows below mightn't be like Money Game, but have an sort of evil ML and he either ends up with FL or it's implied that they might or it's ambiguous:
I think you have already watched Moon Lovers and Cheese in the Trap, but for anybody who hasn't , they seem to fit in a way, depending how you interpret the endings.
My Heart Twinkle Twinkle ( the drama as a whole is kinda annoying, but if you don't mind skipping the ML fits the bill sort of) - whether they end up together or not is very ambiguous
Born Again - he is as gray as you get, the drama is quite dark at times and in my opinion unusual for the kdrama world.
Falling for Innocence- this isn't without the fluff, but from everything I recommended I think the closest to the Money Game imho.
When the Man is in Love - the guy is a loan shark at the beginning - I felt the happy romantic ending was implied but not everybody agrees with me.
Now non of these fit the bill perfectly and some are less so than others, but all of them have gray ML, in some cases more so than others. So I am not sure whether you'd like them, but perhaps check them out just in case ;-)