Once in a while a scene needs something more, a touch of extra emphasis to increase the tension. Usually this means either asking a character to make a sacrifice, or forcing a character to endure and suffer.
Suffering can invoke pity and compassion towards the victim, as well as horror and revulsion towards the perpetrator.
The pain can be physical or emotional. Physical pain is easier to convey, while emotional pain requires more time to establish and earn. The key is to match the intensity to the genre and tone of the story as a whole. A light hearted adventure story shouldn’t suddenly transform into a violent horror or tragedy. Audiences will feel betrayed.
The goal of the suffering is to convey how the suffering affects the character, not to catalog everything that happens, though sometimes that is a valid technique. First make the audience care about the character, then use that connection to convey meaning through the character’s suffering. Show how the character changes, how it weakens the character, and how they recover from it, or fail to recover.
It’s also important to use suffering sparingly, so that the audience doesn’t become desensitized. When someone is hurt, or dies, for the first time in a story, it can be very powerful, but over time the audience goes numb; they disengage, or the audience may refuse to form connections with a character, out of fear that they will simply be hurt again. This is particularly common in horror.
If a character is forced to sacrifice something then the audience may regard it as a form of suffering, but if the sacrifice is made willingly, it becomes a sign of strength. If the sacrifice is for the sake of others the character may become a symbol of courage and altruism, earning the admiration of the audience.
Once again, the key is earning the sacrifice. Establish that the character does not want to make this sacrifice. A character should never be eager to make a sacrifice, or else it loses it’s potency. Show them searching for alternatives, building up the tension as they reluctantly, sometimes grudgingly give in and make the sacrifice.