Regret

Regret may refer to the following:
 * Prophet of Regret - The San 'Shyuum hierarch during the human-Covenant War.
 * Regret (achievement) - An achievement in Halo 2 Vista that is worth 30 gamerpoints and requires the player to complete Regret on Normal or higher.
 * Regret (level) - The ninth campaign level in Halo 2 which requires the player to kill the Prophet of Regret.