Mulan

I am not trying to justify their actions, but it occurs to me that Regina and Rumple both turned to the dark side because they were tired of being victimized, and because they lost someone that they love.
Regina loved her father, but even she pointed out that he did nothing to protect her from her mother. Her mother killed the love of her life, and then forced her into a loveless marriage with a man who essentailly kept her trapped. It is easy to see why Regina would want to take matters into her own hands.
Rumple was considered a coward door pretty much everybody. His wife left him, and it is...