The full name of the Soviet smuggler played by Nikola Djuricko in season 4 of Stranger Things is Yuri Ismaylov.
Yuri is introduced as a Russian pilot and black-market smuggler who helps move American goods into the Soviet Union. He is also connected to Dmitri Antonov, the prison guard who secretly assists Jim Hopper. Joyce Byers and Murray Bauman contact Yuri because they believe he can help them reach Russia and rescue Hopper.
Yuri betrays them for money, drugging Joyce and Murray and planning to hand them over to Soviet authorities. His scheme collapses when they overpower him and force him to help infiltrate the prison. Later, Antonov persuades Yuri to cooperate in their escape. A common mix-up is confusing Yuri with Dmitri Antonov, whose prison alias is Enzo; Antonov is played by Tom Wlaschiha, while Yuri is played by Nikola Djuricko.