Ultimo is, as Stark referred to him, "a standard giant robot". Iron Man defeated Ultimo, blowing it to smithereens. SHIELD then gathered all the parts that were salvageable, and put them in a SHIELD storage facility, designated SHIELD Storage Facility Omega, somewhere in the Appalachian Mountains.
The robot was re-animated by the magic of the Enchantress, and sent to rampage the Avengers on orders from Baron Zemo.