Its hard to find a mirror image of nezzy at the positional end of the tactical/positional spectrum because there is a serious difference between the two ends of the spectrum. The player as close to the positional end as Tal etc are to the tactical end would not be a great player. He would lose against strong players.
Positional Analogue to Nezhmetdinov

Nezhmetdinov never reached the grandmaster level. I wouldn't expect a play who mastered one half of the spectrum to be a great player, compared to those who have relative mastery across both halves. I'm just curious if there exists a player who so furiously embodies positional play as Nezhmetdinov embodies tactical play.
It may be the case that nobody fits the analogue - it seems to me that one can easily play tactically at the expense of position, but playing positionally at the expense of tactics is almost impossible. But I think I'm more on the tactical side, so perhaps I'm biased.

Gosh, I never knew Nezhmetdinov didn't make it to the GM title - I thought anyone scoring a positive result in all his games against world champions should! (Just read the Wikipedia article on him, hehe)
As to being able to be a very strong player solely on the basis of tactics, the Averbakh quotation shows quite evidently that this is not possible. On the other hand, no strong player can do without correct calculation of tactics - Petrosian himself was known to be a true master of calculation.
Still, I think I get what you mean, and right now I am racking my brain who might fit the bill. It seems we are looking for an IM who practically never loses (or lost), not even to world champions, due to his rock solid styl, but never got GM because he repeatedly failed to find the winning tactics even against weaker players. Dunno if there is one single player who can be described this way...
Almost as long as I've known something about historically great chess players, I considered Mikhail Tal the most iconic tactician in recent times, and Tigran Petrosian the most iconic positional player in the same period. Certainly there are other contenders - Kasparov and Karpov come to mind - but Tal and Petrosian seem to embody pure tactics versus pure positional play.
However, I later discovered Rashid Nezhmetdinov - the tactician who spectacularly defeated Tal at his own game, but at the expense of position. Yuri Averbahk is cited on Wikipedia saying:
"Nezhmetdinov, . . . if he had the attack, could kill anybody, including Tal. But my score against him was something like 8½–0½ because I did not give him any possibility for an active game. In such cases he would immediately start to spoil his position because he was looking for complications."
What I've been wondering lately - is there a figure who mirrors this for positional play? Does a well-documented chess player exist who completes the analogy Tal:Petrosian::Nezhmetdinov:<?>