Forty-one people were convicted by a Portuguese court on Thursday of assault and threatening behaviour after a group of fans attacked Sporting Lisbon players and staff in 2018.
But the club's former president Bruno de Carvalho, in charge for five years from 2013, was cleared of any involvement in organising the confrontations.
Nine men were sentenced to five years in prison while 29 others were given suspended sentences. Three more were handed fines.
The attack was carried out at Sporting's training ground in May 2018 after the team had failed to qualify for the Champions League and Carvalho had publicly criticised the players.
Seven Sporting players, including William Carvalho, Gelson Martins, and Bruno Fernandes, cancelled their contracts after the attack.
In an official statement on Thursday, Sporting said the episode was "the darkest day in the club's history".
"These events indelibly marked Sporting and Sporting fans, bringing very damaging consequences for everyone, which shocked the world," the statement added.