Final answer:
A bishop or branch president's main responsibility is to offer pastoral care, provide spiritual counsel, and help a teenager make amends after a confession of sin, supporting their spiritual growth within the religious community.
Step-by-step explanation:
The main responsibility of a bishop or branch president when a teenager confesses sin to him is to provide pastoral care and guidance. This individual is tasked with listening to the confession with compassion and confidentiality, offering spiritual counsel, and helping the teenager to make amends and find resolution in accordance with the teachings and disciplinary practices of their religion. The overall goal is to aid in the spiritual growth and rehabilitation of the individual.