Man, I struggled with this for ages, especially because Ganondorf carries such specific, heavy energy. You can't just slap generic 'enemies to lovers' tension on him. What clicked for me was focusing on the imbalance of power and the sheer cultural chasm between a Gerudo king and a modern reader-insert.
I wrote a scene where the reader character, trying to be pragmatic, offers him a simple glass of water after a skirmish. Not a grand gesture, just water. His pause, the way he studies both the vessel and the offer, lasted a whole page. Is it a trap? A disrespectful oversimplification? A genuine, baffling kindness? The tension lives in him trying to parse a motive he can't map onto his worldview, and the reader desperately hoping this tiny peace offering doesn't get them incinerated.
The physical danger is always there, but the real friction is in the misinterpretations. Let him be intelligent, let him be wrong about the reader's intentions, and let the reader's fear be laced with a terrifying, reluctant fascination with how his mind works. That slow, suspicious re-evaluation is where the heart squeezes.