|It's a threat to all of humanity! Swarm the huge bastard!|
|— Hange Zoë leads an attack on the Colossal Titan|
The Colossal Titan (超大型巨人 Chō ōgata Kyojin?) is one of the Nine Titans and is noted for its incredible size and significant control over the steam emitted by its body. It is currently in the possession of Armin Arlelt. It first appeared in the year 845 during the fall of Wall Maria and later re-emerged in 850 at Trost.
Although all Titans generate enormous amounts of heat and energy when transforming, the Colossal Titan takes this to the next level. The holder can control the energy produced during their transformation to create various effects. For instance, when Bertholdt Hoover attacked Trost, his transformation only caused a wind blast which knocked some cadets over the Wall. However, during the retake of Shiganshina, Bertholdt released an amount of energy akin to a small nuclear device, creating a massive mushroom cloud of dust and rubble, and also ravaging part of the district.
The unique ability possessed by the Colossal Titan appears to be significant control over the amounts of steam emitted by the Titan form. In normal circumstances, Titans emit steam from wounds, and their bodies evaporate completely into steam after receiving a killing blow. The Colossal Titan is capable of emitting great amounts of steam at will. This power can be used for a variety of purposes. By emitting great amounts of steam at once, the pressure and force of the steam will burn and repel any individuals in proximity to the Colossal Titan that are not fixed in place.
However, prolonged use of this ability takes a toll on the Titan, decreasing muscle mass gradually until only the skeletal structure remains. In some cases when it is necessary, the Colossal Titan is capable of evaporating its entire body at once, disappearing instantly. This puts the user in a position of great vulnerability, with no way of preventing a fall from a great height where the Titan form once was. However, this disadvantage can be alleviated if the user is wearing ODM gear.
The Colossal Titan is infamous for its incredible size, standing at a previously unseen 60 meters, high enough to peer over the top of the Walls. Its body mass gives it overwhelming strength, but also makes its movements rather slow.
The Colossal Titan makes its first appearance outside Wall Maria, terrorizing the population of Shiganshina and kicking a hole in the southern gate. Soon afterward, the Titan inexplicably disappears in a cloud of steam. Its actions allow the normal Titans wandering outside to enter Shiganshina, where they begin to feast on its many inhabitants, including Carla Jaeger.
The Colossal Titan reappears five years later in the year 850, breaching Wall Rose so that its brethren can once again devour the humans inside. It is almost immediately attacked by Eren Jaeger, but it first repels and blinds him with vapor from its high-temperature body before vanishing completely from view as it did five years before. This attack prompts the Garrison to enact the Colossal Titan contingency plan for Trost District.
When Reiner, in a moment of exhaustion and desperation, reveals himself to be the Armored Titan and exposes Bertholdt as the Colossal Titan, the two transform into their Titan forms and battle against the Scout Regiment.
As Reiner's Armored Titan battles Eren's Titan, Bertholdt fights against the Scouts with a partially transformed Colossal Titan. When the soldiers are ready to land a killing blow, Bertholdt once more uses his steam emission control to keep them all at a distance, and their ODM gear is unable to reach him in the continuous gusts of wind. Bertholdt's Colossal remains in this state of emission for a short time until Reiner faces imminent defeat in his struggle against Eren and calls for help. Hearing Reiner's signal, Bertholdt falls to the ground below. This causes a destructive explosion below, with the Colossal Titan evaporating into a gush of steam. Bertholdt leaves his Titan, and joins up with Reiner, who had managed to capture Eren in the chaos.
The Warriors fail in capturing Eren and later flee to the ruins of Shiganshina District. For some months, Bertholdt presumably does not use his Colossal Titan until the battle of Shiganshina District, where he prepares to transform into his Titan above the district in order to destroy the city. However, his plan is stopped shortly after seeing Reiner alive and in peril, and he transforms at a later time after speaking with his former comrades. The blast from his transformation engulfs nearly all of the Scouts within Shiganshina and levels the central portion of the district, creating a mushroom cloud.
As the Colossal Titan, Bertholdt begins setting fire to the houses of Shiganshina with his Titan's heat and sends the structures soaring through the air, bringing great devastation to the town. Eren attempts to attack the Colossal, but his attempt is short-lived when he is kicked to the top of Wall Maria. Squad Levi attempts to attack Bertholdt with their Thunder Spears, but the Colossal's steam emission keeps them away. However, at this time Armin Arlelt notices the loss of muscle mass brought on by each steam blast and formulates a plan to defeat Bertholdt.
Armin brings Eren back into consciousness and informs him of his plan to defeat Bertholdt. Knowing his ODM gear will not stay attached to the Colossal's evaporating flesh, Armin grapples to the teeth of the Titan as Eren collapses to the ground below.
Wanting to kill Armin quickly, Bertholdt emits a huge amount of burning steam at Armin, scorching him alive until he can no longer remain grappled to his Titan. Armin collapses to the ground below, and Bertholdt turns his attention to Eren. He notices too late that Eren's Titan on the ground below is in fact merely its hardened shell, and in the moment of vulnerability, Eren, in his human form, strikes at the Colossal Titan, pulling Bertholdt from the nape as the Colossal Titan collapses in defeat.
On the rooftops of Shiganshina, the surviving members of the Scout Regiment are left with the choice of using a Titan injection in their possession to save either Armin or Commander Erwin Smith from the brink of death. The choice is left to Captain Levi, and after some hesitation he chooses to save Armin's life. As a Pure Titan, Armin grabs Bertholdt as he comes back into consciousness and begs for his life. His cries go unheard, and Bertholdt is eaten alive by Armin's Titan, which inherits the Colossal Titan power.