Chelsea was taken away from Abramovich by government intervention over the Russian billionaire's apparent links with Russian president Vladimir Putin.
Abramovich had owned the club for 19 years, but was stripped of the ownership by the government after Russia's invasion of Ukraine in 2022.
"I think it's disgusting what's happened to him," Terry said at a live show of The Obi One podcast which is co-hosted by former Blues midfielder John Obi Mikel.
"What he did in lockdown and what he did for the NHS was sensational, opening up Stamford Bridge to all the nurses and giving people homes during that difficult time.
"He was just a lovely, lovely man who loved our football club and thankfully turned away from one other football club and made the right decision to come to us."
Obi Mikel also said: "Roman was the guy. He cared about everyone; players, fans as well. I remember when my dad got kidnapped and I got a phone call from him.
"He just cared and spoke to me: 'Mikel what do you need, do you need anything, do you know how you can get your dad back? I said: 'I don't know I haven't spoken to the kidnappers yet'. He said: 'OK, listen, with your permission, give me 24 hours, I will go and bring your dad back home'.
"And I was thinking "f***ing hell Roman he's in f***ing Nigeria, you don't know where he is, how the f*** will you get him back, and he was like 'don't worry, I'll get him back'. That is the gangster s***.
"It was just that standard of how he loved the players, his players, and the football club.
"Who we are today is because of Roman, we are Chelsea Football Club. We've won so many trophies, we are one of biggest clubs in world now and it's all down to Roman Abramovich."