Gnarrk is back in the Haney, Tuska and Cardy story from Teen Titans 39 (May/June 1972).
It's not a great story, frankly. The concept of the "noble savage" seems to be at the core of the messy and wandering tale. At the start, Gnarrk is arm wrestling with Wonder Girl, and lets Donna win. But really, shouldn't she win anyway? Gnarrk has caveman strength, but Wonder Girl has Amazonian-enhanced abilities. Anyway, Gnarrk admits that he lost. Lilith has been working with him, and Gnarrk now speaks like an English professor. He no longer wants to use his strength for anything, preferring mind over body.
But then Gnarrk gets fired from his job, when people find out he is a caveboy. He joins Robin, Kid Flash, Wonder Girl, Speedy, Mal Duncan and Lilith as Mr. Jupiter brings them all out to check on some mines he owns in the southwest. They come across a deserted city, and get attacked there. The city was evacuated due to fears of a nerve gas attack, though later we will learn that the poisoned animals were killed intentionally by natives trying to drive out the whites.
The native tribe behind all this has been isolated from the outside world, so another variation of the noble savage idea. They toss the Titans into a cell, and torment and humiliate Gnarrk, for not using his formidable strength.
This works until they attack Lilith. Then Gnarrk loses it, and goes on a destructive rampage. The other Titans get free, but fare really poorly in this story. Kid Flash gets taken down when a woman drops a pot on his head.
In the end, the natives wind up accidentally poisoning themselves, and Gnarrk learns that he has to be prepared to smash people's heads in. Yeah, ok.
Gnarrk does not appear again until the revival of the Teen Titans comic a few years down the road, as a member of Titans West.