Lombardi, 21, was cleared by a jury at Preston Crown Court six months after being charged over an incident that left 53-year-old Cox in a critical condition.
During the trial, the jury was told by Cox's brother, that the Reds fan can no longer sit up or talk following the attack.
"He can't talk, he just whispers," Martin Cox said.
The Italian, who had argued that he had become lost, feared he was walking into trouble and therefore wrapped his belt around his wrist but had not noticed Cox until he had seen him lying on the ground, was jailed for three years for a separate charge of violent disorder, which he admitted in September.
The jury was told that it was not the student but another man who caused Cox's injuries, although footage showed Lombardi, who was in a group of between 20 to 30 Roma fans, apparently swinging his belt in Cox's direction as he fell to the ground.
Recorder of Preston Judge Mark Brown said in his summing up of the case: "Football has been described as the beautiful game but the terrible events that took place outside Anfield stadium when Sean Cox was assaulted, and suffered catastrophic injuries, surely have blighted its reputation."
Speaking to Lombardi he said: "There is no doubt in my mind that your purpose was to cause a violent clash with the Liverpool fans... demonstrated vividly in film footage.
"The footage shows that you had an active role and your assertion in evidence and in your basis of plea that you were just looking for signs for away supporter sections and were suddenly confronted by Liverpool fans is, in my judgement, nonsense."
Liverpool's first-leg 5-2 win over Roma in April was marred by the ugly scenes, which erupted outside the ground before kick-off.
The Reds advanced despite a 4-2 loss in the return leg at Stadio Olimpico, after which Jurgen Klopp's players celebrated on the pitch with a banner bearing Cox's name.