Do-Ten-Kai-Zan

Do-Ten-Kai-Zan (ドテンカイザン) is the Four Generals' ultimate Dai-Gun, a merger of their four Dai-Guns, appearing only in the first film adaptation of the series, Gurren Lagann The Movie: Childhood's End. The full-power of this Gunmen is not truly seen as it quickly is dispatched by the Dai-Gurren and Gurren-Lagann within moments of its appearance.

Mecha
A combining of the Dai-Guns Dai-Gunzan, Dai-Gunkai, Dai-Gunten, and Dai-Gundo, this mecha is the absolute fortress of the Four Generals. However, with Dai-Gunzan having been taken by Team Dai-Gurren, and its General Thymilph killed, the Dai-Gunzan-Du piloted by Viral served as a substitute. To begin the merger, Dai-Gundo appears to spin as a rainbow-coloured cloud engulfs the Dai-Guns. Dai-Gundo then splits in half and attaches to either side of Dai-Gunzan-Du. Dai-Gunkai splits along its length and attaches to either of Dai-Gunzan-Du's upper pair of arms. Dai-Gunten forms into an 'X' shape and the three other Dai-Guns lower down onto it. The final plates slide into place, and Do-Ten-Kai-Zan is complete.

In Childhood's End
After Cytomander was killed by Simon following his re-awakening, Adiane, Guame, and Viral retreated to their respective Dai-Guns, and performed the merger. Do-Ten-Kai-Zan launched a full-on barrage of missiles at Dai-Gurren, but Simon's shield of Spiral Energy protected them. Team Dai-Gurren then used a Giga Drill Break Team Dai-Gurren Special attack that tore through Dai-Gunten, Dai-Gundo (killing Guame), Dai-Gunkai (killing Adiane), and then the Dai-Gunzan-Du (narrowly missing Viral), destroying the ultimate Dai-Gun. Viral was the only survivor.

The destruction of the Do-Ten-Kai-Zan inspired humans across Earth to take to the surface themselves.

Attacks
In its short appearance, Do-Ten-Kai-Zan makes use of all four Dai-Guns' missile ports to unleash a massive barrage of artillery. It is a considerable attack that covers all of the mecha's blind spots, but was unable to harm the Dai-Gurren.

Trivia

 * This Dai-Gun was made to cut on time since the first movie, Childhood's End, is a compilation of the first 14 episodes.
 * The rainbow-coloured cloud to protect the combining Dai-Guns may be an homage to the Final Fusion sequence in another Super Robot anime, King of Braves GaoGaiGar.
 * The official subtitles accidentally mislabel the Do-Ten-Kai-Zan as a 'Dai-Gan', reflecting on the Japanese pronunciation of the 'Gun' in 'Gunmen', 'Dai-Gun', etc.
 * The name "Do-Ten-Kai-Zan" is a combination of the last syllables of the Four Generals' individual Dai-Guns: Dai-Gundo, Dai-Gunten, Dai-Gunkai, and Dai-Gunzan.