Mykhailo Dianov, who was detained after fighting to defend the Azovstal steel works in Mariupol earlier this year, was one of 205 Ukrainian prisoners of war released on Wednesday night.
Back in May, a photo of him flashing the peace sign with his arm pinned together after it was shattered during the Russian siege of the industrial site in the port city went viral.
In it he looks tired and unshaven but otherwise in a reasonable condition.
But the latest photo of Mr Dianov shows him emaciated, covered in scars on bruises on his arm and face.
The group of men Mr Dianov was captured with, who were part of the Azoz military unit, faced four months in Russian prison camps after the battle of Mariupol.
Hardline Kremlin backers had called for their execution, accusing them of being war criminals and Nazis.
Following his release as part of a major prisoner swap this week, he was pictured in a city hospital in Chernihiv with friends and relatives.
He has since been moved to Kyiv Military Hospital, where his sister said he remains in a serious condition and will require long-term treatment.
Alona Lavrushko said shrapnel in his injured arm was pulled out “without anaesthetic, without anything, using rusty pliers”.
The arm is said to be unhealed and missing 4cm of bone due to the inhumane conditions he faced in captivity.
“The doctor in the military hospital has taken a look at him. They’re not going to operate on him just yet; he needs to gain some weight first.,” she told Ukrainian media.
“That’s the main thing because he can’t be operated on in his condition. It could be dangerous for his health. So he has to recover now and gain strength.”
“His physical condition is serious, of course,” Ms Lavrushko added. “But mentally… Mykhailo is very strong. He is extremely happy that he is back.
“He says, ‘I am walking and breathing clean, free air.’”