Krishna used the Sudarshana Chakra to kill Shishupala.
The episode occurs during Yudhishthira’s Rajasuya sacrifice in the Mahabharata. Krishna was chosen to receive the ceremony’s highest honor, but Shishupala, king of Chedi and Krishna’s cousin, angrily denounced him. Krishna had previously promised Shishupala’s mother that he would forgive a set number of offenses, but Shishupala continued his abuse after that limit was reached.
Krishna then released the Sudarshana Chakra, Vishnu’s divine discus, which struck off Shishupala’s head. The weapon is one of Krishna’s defining attributes as an incarnation of Vishnu and appears in many stories as an instrument of divine punishment and protection.
The other options are associated with Vishnu but not with this killing. Rama and Parashurama are separate avatars, while Narasimha killed the demon-king Hiranyakashipu. Shishupala’s death is also significant because he is traditionally identified with a rebirth of Jaya, one of Vishnu’s gatekeepers.