#3 Steaua Bucharest (5 games, 2 wins for Barcelona, 2+1 wins for Bucuresti)
Just like with Nottingham Forest it's difficult to imagine that Steaua Bucuresti was once a European powerhouse.
In 1971 Barcelona faced Steaua Bucharest for the first time in the European Cup's Winner Cup's round of 16. Earlier Steaua Bucharest had beaten a Maltese club by just one goal on aggregate but Barcelona recorded two crushing wins against a Northern Ireland team.
So it was hugely unexpected when the Romanian side won both of the games. These matches didn't attract much interest as for the second match at Bucharest only 5,000 people showed up. Steaua went on to lose in the quarterfinals to Bayern Munich because of the away goal rule.
Six years later Barcelona and Steaua Bucuresti had to face each other again in the first round of UEFA Cup. That time the Spanish team took the matchup completely seriously and won both of the games by a significant margin – 5-1 and 3-1. Barcelona reached the semifinals of the competition but got knocked out by the eventual winners PSV.
The fifth and last game between Barca and Steaua was in 1986. Undoubtedly the biggest match they have played and most likely will ever play between them as it was the European Cup final. The game finished goalless but no one will ever forget the penalty shootout.
While Barcelona's goalkeeper was able to stop the first two shots, Steaua man in the goal Helmuth Duckadam was unbeatable, saving every single penalty. He was later dubbed as "The Hero of Seville" (the place of the final venue).
Steaua Bucharest appeared in the final again three years later but lost by four goals to Milan.