Conflict is the cornerstone of character development. Satisfying resolutions require difficult and/or desperate conflicts. A persons true self will come out to either overcome or be crushed by adversity. someone under pressure will reveal their true selves and if done right, the audience with empathize. "I know what the feels like", or "I can only imagine what that must feel like." Truly, the substance of your personality, youre "raw self" peeks even a little bit when engaged in an argument. and in that moment, in the audiences mind, you become a simple archetype. You are clarified because a dominate emotion has taken over you, even if you remain calm during huge events.
It all has to still feel possible or some way imaginable to relate to, otherwise the viewer is pulled out of the story and no longer cares what happens at all. The tendency is to make the conflict as intense as possible, or the antagonist as even as possible. Keep in mind that the situation or bad guy still has to make sense. Not to say that you have to oversimplify, it just has to seem plausible for the situation to happen or the villain to exist.
On top of such constraints, the unpredictability of the outcome has to be maintained. I dont mean whether or not the protagonist succeeds or fails, but rather how he does so. ill come back to it, im out of juice.