Doomed State is the state that a Titan is put into, once its base health and shields have been removed. When a Titan is in Doomed State, the health bar is replaced with a striped black and yellow bar, signifying to the player of the Titan's health. External changes will also appear, with the Titan's chassis being shown as charred, on fire and badly damaged. These changes are irreversible and once a Titan has been Doomed, it cannot be un-doomed (the sole exception being the Monarch Titan, whose Survival of the Fittest kit allows Batteries to repair out of Doomed State).
In Titanfall, the health bar will slowly erode over the course of several seconds, meaning the player must eject immediately or die in their inevitable explosion. In Titanfall 2, the Doomed State will not automatically erode, and a smart Pilot can survive in Doomed State for the entire match if they minimize damage to their Titan. However, the new rodeo system means that a Pilot who is succesful at removing a Battery or throwing a Frag Grenade in the exhaust will instantly kill a Doomed State Titan, regardless of how much health the Titan has left.
Additionally, any Titan that is in the Doomed State is in risk of being Terminated. At the launch of Titanfall 2, this risk could be put aside as long as the Titan in question had any amount of shield remaining. However, as of Monarch's Reign, any Titan in the Doomed State can be Terminated, regardless of shield status.
In Titanfall 2's version of Frontier Defense, a special Amped Battery can be purchased between waves to bring a Titan out of the Doomed State. Fully repairing a Titan in this manner is very expensive though (each battery costs 500 credits, and several are necessary to bring a Titan back to full health) and so Pilots may prefer to sacrifice their Titan and redeploy at full health at a later point, especially if they possess a Nuclear Eject system.
In Titanfall: Assault, Doomed State functions as it did in Titanfall 1, with a doomed titan gaining a new health bar that decays 10% every second, as well as being prone to being Terminated, though currently only heroic Titans such as BT-7274 and a charged Core Ronin can do so. The Nuke Atlas begins the detonation sequence as soon as she enters Doomed State.