#3 Olympique de Marseille
It might seem uncharitable to include the only French club to have ever won the UEFA Champions League in this list, but there is no doubt to their underachievement in Europe. Considering their status as one of Europe's best teams during the 1980s and 1990s, Marseille should have done much better in European competitions. They dominated the French league for a considerable period of time and were quite good in the UEFA Champions League during the early 1990s.
They were runners-up in 1991 and two years later in 1993, Marseille beat favourites AC Milan to lift the coveted trophy.
However, since then, they reached the knockout stages of the competition plenty of times and over the years had plenty of notable players in their squad but could never make it big. In 1999, they were runners-up in the UEFA Cup and five years later they ended up on the losing side in the final once again to continue their wretched run in Europe.