Some TMNT stuff was always meant for grownups.
Barney Runningbear was born in Seattle, Washington and grew up on a Native reservation. Nuclear waste had been dumped nearby for years, and one day when he was but eight years old, the waste contaminated the reservation's water supply, killing all of its residents. Barney alone survived, due to a genetic anomaly that mutated him instead of killing him. He was adopted by a family in Everett, although the rioting neighbors, appalled that a freak lived among them, drove him to run away.
Eventually Barney made his way to Chicago and started going under the name Barbaric as a superhero.
Involvement with the TMNT
Barbaric had an action figure released in the Teenage Mutant Ninja Turtles/Savage Dragon mini-line and was featured in the pack-in comic. The Ninja Turtles also made a cameo in the crowd of Barbaric's wedding in The Savage Dragon issue 41.