His brain was "rotting away" from degenerative disease CTE which had started years earlier and ramped up to a "horrific finale", his sister Renee Tuck told an inquest into his death on Friday.
Tuck, who played for Richmond and then became a professional boxer, took his own life at the age of 38, in 2020, after a long period of mental health decline.
His family only discovered he had CTE after donating is brain to the Australian Sports Brain Bank after his death.
They had noticed his mental decline years earlier, as far back as 2006, and Ms Tuck said they would never have received any closure if experts had not examined his brain.
"Shane's brain was riddled with CTE lesions - he had the worst diseased brain Professor Michael Buckland had ever seen," Ms Tuck told the Coroners Court in Melbourne.
"He pushed through hell to stay with us as long as he could and in his death he found his peace, but our agony at living without him began."
She said he "worked his arse off" while playing for Richmond, to make his team and coach proud, but the last coach he had as an AFL player did not reach out to the family after he died.
This, she said, "speaks volumes of how his continuous grit and determination went unacknowledged".
"If not for CTE, Shane would have lived a long life because he looked after himself so well," Ms Tuck said.
"He would have lived to see his kids grow up."
Victoria's State Coroner John Cain is investigating the link between Tuck's concussions from repeated head knocks while playing AFL and boxing, and his brain injury.
The inquest has heard evidence from world-leading brain injury expert Robert Cantu, Professional Boxing and Combat Sports Board chair Alan Clayton and the AFL's chief medical officer Michael Makdissi since it began last week.
Dr Makdissi, who appeared earlier on Friday, revealed the AFL was close to developing a helmet for players to protect them from head knocks and concussions.
"It may be deployment of a helmet is suitable in either the next season or the season after, so it's close," he said.
But he said helmets would need to be tested first to ensure there are no "unintended consequences" on the game.
Dr Makdissi said the league was also trialling mouthguards fitted with sensors, to allow head impacts to be measured while players are on the field.
The trial, which has been made available to all clubs, will be completed by the end of this season, he said.
The inquest continues.
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