The 26-year-old -- who won bronze for France in the long jump at last month's world para athletics championships in London Stadium -- was just three when he and his family, who are Tutsis, fell victim to the onslaught of the majority Hutus in 1993.
Eight of his family, including his mother, were hacked to death whilst he suffered four serious wounds, to his wrist -- which was so deep a cut he was fortunate not lose his hand -- his head and back, all of which still bear the scars.
However, that was not the worst of it as surgeons had no option but to amputate the lower part of his right leg.
"I was all but dead for a week," he told AFP by phone before flying to Burundi for the Friendship Games which get underway on Friday and where he will speak to a couple of hundred children from Burundi, Rwanda and the Democratic Republic of Congo about his experiences.
"I suffered serious internal hemorrhaging as a result of the four machete cuts and lost so much blood.
"They (the nursing staff) thought I had died on several occasions but I defied the odds and was out of danger by the end of the first week.
"That's how I earned the nickname 'The Lion'."
Alaize, who spent five years in a Bujumbura orphanage where his father had abandoned him and failed to tell his three sisters he was still alive, doesn't recall much of that appalling experience or indeed his mother, save for one thing.
"I was her pet, I remember being given all the attention," he says.
"I recall her whispering in my ear that I was her favourite."
Life changed for the better when aged eight a former French soldier Robert Alaize -- who had coincidentally lost a leg in an accident -- visited the orphanage and along with his wife Danielle adopted him.
- 'Sport changed my life' -
There he says he was brought up in a loving household along with his 'brother' Julien who comes from Rwanda and was also adopted by the couple, who also foster children in difficult circumstances.
"They gave me a lot of love and encouraged me in taking up sports," he said.
"Although I went to a psychologist to help me through the trauma it was through sports that I really found the most therapeutic remedy.
"Sports changed my life, I only knew death before I encountered it."
He proved proficient at horse riding and cycling but his real talent came in track and field with four world junior titles in the long jump plus several minor medals in the sprints.
"It was a very proud moment for me to win my first title, standing there and reflecting on how far I had travelled," he said.
Alaize, who enjoyed an emotional reunion with his three sisters in Burundi in 2013 after Danielle tracked them down and they visited the spot where the massacre took place and where his mother's body was dumped, says returning to the country of his birth gives him little pleasure.
Alaize was not even able to learn much about the circumstances of the massacre -- save that he had been attacked once he fled the house which no longer exists -- as the perpetrators still live in the vicinity and were never prosecuted.
"I know more about the war than the culture of the country," said Alaize.
"I am going for the event (the Friendship Games) and not for holidays.
"It is sports that has me going back there.
"For me France is now my country not Burundi."