The 34-year-old finally banished years of personal problems, which included a spell in a Spanish prison, and showed he still had the punching power that saw him enjoy numerous world title defences in his heyday.
The Scot looked in impressive shape and put the previously unbeaten opponent down four times before the referee stopped the International Masters lightweight contest amid concern over a blow to the head.
Harrison, making his first appearance since a successful defence of his WBO featherweight title against Nedal Hussein in 2005, came out to a huge ovation from the crowd at the Kelvin Hall in Glasgow and was immediately on the attack against the tall but slim Hungarian, who has won seven professional fights.
Harrison put together several good combinations in the opening round without seriously troubling his opponent but he had him down three times in the second, on each occasion after a left hook to the body.
Harrison remained on the attack in the third with a right hook to the head his most dangerous weapon and it seemed a matter of time before the Scot finished off his opponent, who was a late replacement for Frenchman Brahim Bariz, who pulled out on Tuesday.
That time was midway through the fourth when a succession of right hooks forced the stoppage.
Harrison relinquished his belt in 2006 after failing to make the weight for a defence and checked into the Priory Clinic in Glasgow to treat problems with alcohol and depression.
The Cambuslang boxer lost his licence and continued to struggle with personal problems, and served two-and-a-half years in a Spanish prison after being found guilty in 2009 of assault and attempted theft of a car in Malaga three years earlier.
Harrison, who won a long battle to regain his licence in December last year, said: "It was a privilege to be out there in front of the fans.
"I want to thank them for coming out to support me.
"Throughout my suspension I have always kept myself in shape no matter what you read in the papers about me being at death's door.
"Hopefully I'll get a chance for a world title in the near future.
"In the past I was training to lose weight but now I'm improving my fitness and strength.
"As the fight went on I was punching harder."