What do I do when I realize I've been trying to win over the executive who's actually undermining me?

Stop trying to win them over. Replace them. Kris Kluver, in The Dysfunctional Family Office, captures the moment Gail Mitchell figures this out about Brett, her CFO. She had been bending over backwards to convert him. Brett had been quietly telling clients Gail wasn't ready and didn't deserve their full trust. The realization landed like ice water. He had been fighting her from day one. She had been trying to win him over instead of replacing him. The pattern is common. Most rising generation CEOs keep trying with longtime executives because the founder is still around, the executive built the company, and replacing them feels disloyal. The actual disloyalty is letting the saboteur destroy the company while you protect the relationship. The fix is hard and direct. Have one honest conversation about expectations. If the behavior continues, replace them with dignity. The longer you wait, the more damage they do.