Some TMNT stuff really isn't for little kids.
Colonel Ch'rell appears in the IDW comics as one of the Utroms that, since the initial exile of his race, is sleeping in stasis in the Technodrome. Ch'rell is an Utrom discussed by Professor Zayton Honeycutt as being Krang's deadliest warrior and just as guilty of war crimes as his superior officer. He is described as one of the few Utroms with a natural propensity for violence. For this reason, Honeycutt decides to hold off on reviving Ch'rell from stasis until after he is able to talk with the other Utroms.
With the death of Krang at the conclusion of The Trial of Krang, two Utrom soldiers discuss their clandestine plans to awaken Ch'rell in his stead, as some Utroms still believe in Krang's cause of conquest and disapprove of Ma'riell's peaceful Utrom leadership.
While Honeycutt views him as deadly threat, Ch'rell is not seen as a menace, threat, or anomaly by many of his fellow Utroms; indeed, they speak of him highly and were surprised to learn that he was still in stasis instead of being awakened just like them.
Ch'rell and the current Utrom leader Ma'riell are brother and sister, though Ma'riell disapproved of Krang and Ch'rell's pursuit of conquest and genocide as a means of sustaining their race.