The crash at Meenaduff, between Buncrana and Clonmany in July 2010 was Ireland's worst ever road accident.
Hugh Friel, 66 and seven men, aged between 19 and 23, died in the crash.
Shaun Kelly, of Hill Road in Buncrana, had previously pleaded not guilty to charges of dangerous driving.
Seven of the victims were travelling in the same car.
They were 21-year-old Mark McLaughlin, from Fahan; Paul Doherty and Ciaran Sweeney who were 19 and from Ballyliffin; Patrick McLaughlin, 21, from Burnfoot; 22-year-old Eamonn McDaid and 21-year-old Damien McLaughlin, both from Buncrana, and James McEleney, 23, from Clonmany.
Father Michael Sweeney said the end of the court case would "bring a little closure to the families".
"It will take years for them to come to terms with their great loss, but this court case has been pending for the last four years," he said.
"For them, each time it came up for review, it was like revisiting the scene of the whole bad experience and trauma of the terrible event.
Kelly was driving a black Volkswagen Passat with the seven passengers when it collided with the car driven by Mr Friel.
He was the only survivor of the crash and sustained serious injuries.
He changed his plea as the jury was being sworn in at Letterkenny Circuit Court on Tuesday.
Fr Sweeney said: "It was a brave thing for him to do, to plead guilty to dangerous driving, and I feel sorry for him that he has to live with the consequences of that for the rest of his life.
"The whole community was totally shocked - it was one funeral after another, and each one of those traumatised the whole community who turned out to support those people."

It is alleged in journalist Matthew d'Ancona's book that Larry is merely a public relations prop.
But a Downing Street spokesman said Larry was "very popular with everyone" in the building.
His lackadaisical approach to mousing has previously led to speculation he would be relieved of his duties.
Larry was brought in to catch rodents, but he was spotted asleep on the job for several hours back in November 2011.
Downing Street confirmed last year, though, that the six-year-old rescue cat - who was re-homed from Battersea Dogs and Cats Home in February 2011 - had recorded his first kill.
Following the latest claims in Mr d'Ancona's book about the inside story of the coalition government, called In it Together, a "savelarry" hashtag became popular on Twitter.
But on Saturday a spokesman for the prime minister said the allegations that Larry was not liked were "totally untrue".
"He is very popular with everyone in the building and we all get on purr-fectly well," he said.
On Saturday, Ladbrokes today gave Mr Cameron 1/2 odds of leaving Downing Street first with Larry the cat on 6/4.
Jessica Bridge of Ladbrokes said: "This is a new low for Cameron during his time as PM, and despite his dislike for the cat, we favour Larry to outlast him at Number 10."
A man's guilty plea to causing the deaths of eight men in a road crash in County Donegal has spared their families further trauma, a local priest has said.
[NEXT_CONCEPT]
Number 10 has denied claims in a new book that Larry the Downing Street cat is disliked by the prime minister and his family.