Some TMNT stuff was always meant for grownups.
Dr. Raven Shadowheart, best known by her nickname Radical, was given the power of liquid energy when she was struck by a lightning bolt. Using these powers for good, she battles her arch-nemesis Complete Carnage, who was a construction worker that was struck by the same lightning bolt. She appears in the Mirage Comics series.
Raven grew up on an Indian reservation, and she once had an encounter with a boy who did chores for her grandfather where they were at a river and he threw a rock at a beaver. Raven later realized that this boy who angered the beaver god would turn out to be the man named Complete Carnage. One of Radical and Carnage’s earliest confrontations occurred when Casey Jones and Raphael stumbled into him while entering a building they thought abandoned. Radical appeared and, after a short fight, flung him halfway across the world (Shell Shock).
Another confrontation occurred when Carnage appeared when she was biking, surprising and nearly overtaking her. Now possessing the ability to pass through and absorb into man-made things, Carnage posed an even greater threat. Pulling off his arm, Radical lured him away, then used her "Particle Beam" ability, scattering their atoms and eventually warping them both to the ethereal-like "Dreamscape" (Tales of the TMNT #5). Radical and Carnage sparred for the final time when she sought out Carnage, having the Turtles distract him while she prepared a spell that liquefied the road Carnage attempted to dive into, liquefying (and killing) him in the process (TMNT Vol. 1, #27).
It seemed the arm Radical pulled from Carnage’s socket got into the hands of the Whelan-Freas Scientific Research Center. The center generated a clone of Carnage from the arm, a clone that escaped to go on a rampage in Chicago. The Turtles, learning of this, sought Radical’s help, who they found to now be going by her Native American name, Raven Shadow Heart, a teacher who then worked toward preserving her culture at the Museum of Natural History in New York. She was unable to intervene against Carnage because she did not have permission from the "Council," (because the creature rampaging was a clone, not the real Carnage—the being she was destined to fight and had already beaten) but the Turtles were victorious nonetheless with the help of Officer Dragon (TMNT/TSD II & TSD series #22).
- In Transdimensional Teenage Mutant Ninja Turtles, Radical is given the real name of Hazel McIntyre and a very different character background and origin story. None of this is corroborated in the Mirage Comics themselves, where her name is given instead as Raven Shadowheart.
- In Dreams of Stone, Radical emphatically rejects the notion that she is a superhero.