How do I coach managers who resent me or refuse to change?

You can coach the managers who want to grow, and that is most of your success. The ones who resist or resent you defeat you because coaching only works with a willing person, and no skill of yours can manufacture willingness in someone who has decided against it. That is the hard, freeing truth: their change is not yours to force. You can offer, invite, and create the conditions, but you cannot want it for them. When you take their refusal as your failure, you carry a weight that was never yours. Some people are not ready, and that is about them, not you. With a resistant manager, shift your aim from changing them to understanding why they resist, and ask them directly what would make this worth their while. Sometimes the resentment hides a real fear you can meet. And sometimes the honest move is to accept that not everyone can be reached by you, right now, and spend your energy where it lands.