[1] Comic Book Resources rated Ultimo at #10 on their list of "Marvel's 10 Most Powerful Giants," referring to him as "a doomsday weapon created by a long-destroyed alien culture.

"[2] Ultimo is a gigantic ancient android of unknown origin who is believed to have been created by an alien race as a doomsday device.

The only survivors, a group of Rajakian merchants who were off planet at the time, lure Ultimo into an asteroid belt, disable him, and allow him to crash-land on Earth.

[volume & issue needed] Ultimo vanquishes a force of Chinese soldiers sent to dispatch the Mandarin and nearly destroys Iron Man, but is drawn back into the volcano.

The then-current version of Iron Man (the remote-controlled NTU-150) proves no match for Ultimo, and is torn to pieces — and the cybernetic backlash to the nervous system renders Tony Stark comatose.

Since Iron Man's armors would not function anywhere near capacity (having been stored for sentimental reasons only with the idea of never being used again), Rhodes decided on a change of plan against Ultimo.

Having performed extensive research of the hulking, inert robot, Stark-Fujikawa's engineers managed to access its control programs, and now the company intends to use the enormous energy reserves stored inside Ultimo to provide cheap electricity to the entire Western USA.

[10] The ship built on top of the dormant doomsday device is attacked by Goldenblade and Sapper — ironically, representatives of the doomed Rajaki race, seeking to steal energy to resurrect those Rajaki that still survive as data patterns aboard the crashed vessel - who accidentally wake up Ultimo, and the robot immediately sets out to destroy the ship.

[volume & issue needed] Afterward, Ultimo is dismantled and his systems "fried" by the transfer of his energy stores to the Rajaki vessel.

[11] Ultimo reappeared, apparently fully restored, facing the Mighty Avengers - just long enough to be deactivated by a single shot of the Tactigon, a weapon of unknowable power (at the time) in the hands of a girl called Armory.

War Machine renders Ultimo docile by forcing Norman Osborn into showing memories of respective happiest moments.

[15] Ultimo (having had his core programming erased) turned into a giant, floating ball of liquid metal that was essentially awaiting instructions.

[16] But on War Machine's request, drops of Ultimo infected the nefarious "Bainesville Ten" group to see recordings of every person who was raped, tortured or killed from their own orders.

After Stark-Fujikawa's engineers accessed his systems, he is made to grow to "over a hundred feet" (he stretched along the entire length of the hull of a medium-sized research vessel).