All four Greysteel killers were freed from jail in 2000 under the terms of the Good Friday Agreement.
Gang member Torrens Knight, who was 24 at the time of the attack, had been given 12 life sentences for his role in the murders and those of four Catholic workmen in nearby Castlerock.
Last week he apologised for the first time for his role in the massacre and told the Belfast Telegraph he deeply regretted his involvement in the killings.
Days before the 20th anniversary of the atrocity, he said: "I am sorry."
The 44-year-old added: "My thoughts and prayers are with the victims and their families. But there's nothing I could say would help.
"The victims are the ones who have to carry on with life and they are still paying the price.
"That's how I feel.
"At the end of that day it shouldn't have happened, it was a terrible thing. I wish all the atrocities didn't happen."
The other three killers have never demonstrated any remorse for their actions.
SDLP MLA John Dallat, a friend of some of the families of those killed, dismissed Knight's apology as "too little, too late."
Part of an increasingly sickening upturn in tit-for-tat sectarian killings at the time, the shootings at the Rising Sun bar were mooted by loyalists as revenge for an IRA attack on the Shankill Road the previous week.
Nine people, including two children, were killed in the bombing of Frizzell's fish shop.
The cycle of slaughter in the era prompted genuinely held fears that Northern Ireland was lurching towards an all-out civil war.
Instead, the killings proved to be the final catalyst for politicians on all sides to re-double their efforts to begin on the road to the peace process, a fact tragically reflected on a memorial outside the scene of the Greysteel shootings which states: 'May their sacrifice be our path to peace.'