Well, i cannot claim to have a strong penchant for the Sopranos (due to time constraints) and thus i cannot answer that question. However based on what i know about the Spetsnaz forces (especially the ultra spetsgruppa al'fa) the Spetsnaz operator Paulie Walnuts failed to kill is definitely going to come back and seriously mess up Paulie boy's natural life span in a seriously detrimental way. That is if the show tries to be 'realistic.'
After all the real Spetsnaz are typically ruthless in action. For example in 1985 some PLO terrorists (then based in Lebanon) kidnapped several Soviet officials and held them hostage in the Soviet embassy in Beirut. The terrorists were given 48 hours to let the Soviet officials go, but they answered it by letting the deadline expire and then killing one of the officials.
That was when the Spetsnaz were sent in (the particular group was the spetsgruppa al'fa) and they immediately kidnapped several of the terrorists, together with several family members (of the terrorists). Then they cut of the heads of the captured terrorists, together with the heads of their family members, put them in a duffel bag, and sent them to the chief terrorist with a promise of further unrestarined action! The hostages were promptly released.
The Spetsnaz are primarily ruthlessly efficient (in Soviet times they used to practice their 'systema' combat techniques on prisoners in the Soviet Gulags since they could practice the techniques on real moving human bodies at full force with no fear of punishment).
Anyway, pitting Paulie Walnuts against a Spetsnaz operator, and Paulie failing to kill him the first opportunity he had, means that the Spetsnaz guy is gonna come after Paulie and make him swallow his b@!!$.
End of story!
P.S: Nowadays most of the Spetsnaz (spetsialnoye nazranie) units have fallen into problems due to the problems afflicting Russian military spending, however several Spetsnaz groups (the best) have been maintained at perfect fighting ability, and one of these super-spetsnaz groups is the Spetsgruppa Al'fa. (One of the reasons that Islamic groups never mess with Russia, and those that do ...like the Chechnyans separatists.....never push the envelop too far. For example when they planted a 'dirty bomb' device at Grozky park they immediately allerted the authorities to ensure they defused the bomb before it detonated! Obviously they knew that exploding any type of radioactive device in Moscow would have made the Russians immediately send nukes at the perpetrators ...and i doubt Russia would have bothered asking the UN for 'assistance.' )