qnli question: What Greek volleyball club is the most successful in the country? sentence: Olympiacos is the most successful volleyball club in the country having won the most domestic titles and being the only Greek club to have won European titles; they have won two CEV Cups, they have been CEV Champions League runners-up twice and they have played in as many as 12 Final Fours in the European competitions, making them one of the most traditional volleyball clubs in Europe.