Dying Will Mode (also known as "Deathperation Mode" by the fucking autists at Viz Media), is a transformation present in the anime series, "Katekyo Hitman Reborn" and Neo Scary Godmother.
If someone has a lingering regret before they die and are hit by the Dying Will Bullet (or by ingesting a Dying Will Pill), the user will be 'reborn'; gaining immense strength and resolve (losing their clothes in the process). The body's external limiters are removed in order to maximize durability and stamina, exponentially increasing the user's overall power.
This ability can also be triggered at will if mastered, not requiring any outside help. If untrained, the huge strain of stamina on the body will only allow this form to last 5 minutes, and can dissipate if too much damage is sustained in battle. Training oneself to sustain the form for over the 5-minute limit is a prerequisite to utilizing the successor transformation; Hyper Dying Will Mode.