The New-Raboot-X is a giant rabbit robot created by Dr. Weird with the objective of destroy the world and replace the other Raboot that he created a long time ago.
Dr. Weird was searching a new plan to create a new creature that destroy the world, then Steve tolds him about a "new raboot" then Dr. Weird prepared the plans with Steve to create The "New-Raboot-X. Dr. Weird used Hirohito's Brain to create for him an intelligence from somebody evil like Dr. Weird and used Chuck Norris arms to make him more handsome. Being Hirohito, Raboot-X can't say anything other than "Duncan" because he was his killer when he was Hirohito in the destroyed SSS Squad. Steve shortly believe create it was a bad idea, then the New-Raboot-X slapped Steve away.
After that and now with the help of Satan, Dr. Weird and Raboot-X captured Duncan but Duncan without effort destroyed New-Raboot-X. Dr. Weird and Raboot-X fused to fight Duncan once more but they were defeated and Duncan cut Raboot-X's head off, killing Hirohito for good in the process. Duncan later kept Hirohito's brain as trophy.