Whether the intensity is emotional or physical, focus on the :

In high-tension scenes, what isn't said is often more powerful than a confession.

Establish why these characters are falling for each other at this specific moment of crisis [1].

Don't skip the "cooldown." The period after a major conflict or intimate moment is where the most significant character growth occurs [3].

Characters who have everything to lose (reputation, career, safety) by being together [1].