Oh, this is actually one of those messy power fantasy serials where the 'antagonist' shifts a lot. Early on, it’s clearly Richard Klein, Danni’s biological father and the CEO of Klein Corporation. He's the classic abusive patriarch who sees her as a tool, orchestrates her marriage, and is the source of her initial brokenness. He represents the corrupt corporate and familial power she has to escape.
But as the story goes on, the real sustained opposition comes from Angela, Richard's favored daughter and Danni’s half-sister. Angela is obsessed with status and being the perfect heiress, and she orchestrates most of the direct, petty schemes against Danni—the public humiliations, the stolen credit, the romantic sabotage. She’s the face of the daily antagonism, while Richard is the systemic evil behind it. Honestly, by the midpoint, I was way more annoyed by Angela's constant meddling than Richard's distant cruelty.