Do you mean Roman Dzindzichashvili?
Yup, it was Roman.
I played him oh gawd ages ago, something like the 1982 Chicago Open. I had to play him in the first round (one of those unlucky accelerated pairings) and had one of the most excellent "central pawns blocked solid by active pieces" positions I think I've ever had. Something like his (black) pawns on d4 and e5, blocked by my knight on e4 and a bishop on d3. My knight controlled a lot of important squares, my bishop protected others; he had a bad fianchettoed bishop on g7 and I had a good passed pawn on the queenside. After twenty years, I forget what exactly went wrong, but I had him sweating for a while... if I remember correctly, I think I even made the time control with an advantage, but I collapsed soon after that. Alas, as a GM he was quick to exploit my mistake (whatever it was) after a hard 5-hour fight.
The irony was (if I remember correctly) he lost in the next round. I console myself by thinking I tired him out for his next opponent. :=(
I think the best player I've ever actually beaten was a 2405 IM from Brazil in the 1986 World Open.
"Beware of bugs in the above code; I have only proved it correct, not tried it."
-- Donald Knuth