Jake Vallely, 24 - who had described himself as "the hardest man in Brecon" - beat 20-year-old Private Matthew Boyd to death in May.
Pte Boyd's mother Michelle Rogers said her son's death had caused "unbearable pain".
At Cardiff Crown Court on Thursday, Mr Justice Lewis said the killing was a "savage and senseless attack".
Vallely was found guilty of murder on 1 December following a two-week trial.
After a night of drinking, the former boxer had pursued Pte Boyd through the Powys town before carrying out what Mr Justice Lewis described as a "sustained attack on a young man lying defenceless in the road".
Pte Boyd, who is originally from Carrickfergus, County Antrim, had been in the town for training exercises at the infantry battle school.
Sentencing Vallely, Mr Justice Lewis told him Pte Boyd was "entirely innocent and did not provoke you in any way. You chased him down and attacked him for no other reason than you wanted trouble".
The judge said: "You hit him time and time again until he was unconscious. This was a sustained, savage and senseless attack.
"You dragged his motionless body into the street and left him there to die. You showed no remorse then and you have shown no remorse since."
Members of Pte Boyd's family were not in court today for the sentencing.
They have returned to Gibraltar where they live, but victim impact statements were read out during the sentencing.
His mother Michelle Rogers said: "His life was taken in the blink of an eye. My son will not knock at my door again. There are times I text or call his mobile. I cry every night before I sleep, if I sleep. How can I explain the pain in my heart?
"It is unbearable, he has taken my son's life and destroyed our family."
His stepfather Jeremy Rogers said: "I don't want the pain to go away because if the pain goes away, so will Matthew."

Varnish, 25, alleges Shane Sutton told her to "go have a baby" after she was dropped from the British team.
Rowsell Shand insists the sport's governing body treats the women's and men's endurance squads identically.
"I've always thought, as a track rider, it's very equal," the 27-year-old said.
"Compared to the men's team pursuit squad, we definitely get equal treatment."
Sutton denies making sexist comments and says British Cycling did not renew Varnish's contract because her times had slowed over the past three years.
Dani King, who raced alongside Rowsell Shand in the 2012 gold medal-winning pursuit team before switching to road cycling, said she had "never encountered" anything sexist.
Speaking on BBC Radio 5 live's Afternoon Edition, she added: "Shane's a no-nonsense sort of guy, he tells you how it is, but I never had any of those comments made towards me."
Team sprint rider Varnish has been been invited to meet the equalities officer of British Cycling to discuss her concerns.
Road race world champion Lizzie Armitstead defended Varnish's right to publicly comment about any perceived injustice.
"Any athlete in her position has the right to say what she said," said Armitstead, 27.
"She's worked so hard to be in the position she's in and to have that taken away from her, if she feels that it's unjust, then she should speak out about it."
Armitstead, who won road race silver at London 2012, is now based in Monaco and no longer works with British Cycling on a day-to-day basis.
"I haven't operated within British Cycling for a very long time," she said. "I've had to forge my own path, because I needed to."
Varnish, a world, European and Commonwealth Games medallist, missed out on qualification for the 2016 Olympics in Rio de Janeiro after she and Katy Marchant finished fifth at last month's World Championships.
She subsequently criticised British Cycling's coaches for their selection policy during the qualifying period, telling BBC Sport she and Marchant "had been playing catch-up for two years" because of decisions made "above us".
A Brecon man who murdered a soldier in the town has been sentenced to life with a minimum of 16 years in prison.
[NEXT_CONCEPT]
Olympic gold medallist Joanna Rowsell Shand says she is "surprised" at Jess Varnish's claim British Cycling's technical director made sexist comments to her.