The Russians may have their own gifted children in Stranger Things. Stranger Things has always existed in the shadow of the Cold War; in the real world, the MKUltra Project that inspired the show was an anti-Soviet psyops project.
The Cold War finally came to Hawkins in Stranger Things season 3, when Hopper discovered a dark conspiracy between the corrupt Mayor Kline and a secret Russian black ops project. The Russians had learned of the Upside-Down, and they'd realized that it could only be accessed in Hawkins. With Kline's help, they constructed a new Gate generator beneath Hawkins, but fortunately in Stranger Things season 3, episode 8 Hopper and Joyce were able to shut it down. But tie-in comics are suggesting the scale of the operation was never truly revealed.
The Stranger Things: Six miniseries tells the story of some of Dr. Brenner's other test subjects at Hawkins Lab, including a precog whose real name is Francine. In one key scene, Brenner tells Francine that there are other facilities conducting exactly the same kind of experiments on children with psychic potential. As manipulative as Brenner may be, it would make sense; even in the real world, MKUltra was a mirror of psyops projects being conducted by the Soviets. Presumably the same is true in Stranger Things as well.
Brenner's reference to a "war" confirms that he's talking about rival projects being conducted on the other side of the Iron Curtain. Clearly these projects never learned how to open a gateway to the Upside-Down; if they had, the Russians would never have needed to come to Hawkins in Stranger Things season 3. But that doesn't mean they couldn't have unlocked psychic talents in children, creating super-powered weapons of their own. The various Stranger Things tie-ins have covered everything from pyrokinesis to psychic manipulation, so who knows what these Russian agents could be capable of?
This comment may also support a popular theory that Brenner has joined the Russians. Although Brenner survived his apparent death in Stranger Things season 1, he's on the run from the very children he trained. For all her skill and powers, though, Kali has been unable to track him down in order to get revenge on him. That raises the intriguing possibility that Brenner has turned traitor and joined the Russians, hiding from Kali on a completely different continent, on the other side of the Iron Curtain.
After all, if the Russians really are interested in psychic children and the Upside-Down, Brenner would give them a lot of useful intelligence. And that would perfectly position for a major role in Stranger Things season 4, which looks set to head to Russian soil.