Final answer:
Caravaggio employs chiaroscuro in the Crucifixion of St. Peter to create tension.
Step-by-step explanation:
The artistic technique that Caravaggio employs in the Crucifixion of St. Peter to create tension is chiaroscuro. Chiaroscuro is an artistic technique used during the Renaissance that refers to the use of exaggerated light contrasts to create the illusion of volume. Caravaggio's painting utilizes deep darkness and dramatic light contrast to enhance the emotional intensity of the scene, emphasizing the anguish and suffering of St. Peter.