The WNBA superstar told ABC News' Robin Roberts in a lengthy interview that aired Wednesday night the thoughts crept into her mind just after Russian authorities threw her behind bars for packing vape cartridges in her luggage at a Moscow airport in February 2022.

"I wanted to take my life more than once in the first weeks," Griner said. "I felt like leaving here so badly."

The 33-year-old told Roberts, though, she didn't go through with it ... out of fear that her body wouldn't be released to her family.

"I can't put them through that," she said. "I have to endure this."

Griner said while imprisoned, she faced awful living conditions ... explaining to Roberts her mattress had a big blood stain on it -- and there was minimal toilet paper and no soap in the bathrooms.

She added that at one point, Russian officials made her pen a letter asking for forgiveness and "thanks from their so-called great leader" Vladimir Putin.

"I didn't want to do it," she said, "but at the same time, I want to come home."

As you know, Griner was sentenced to nine years in Russian prison on drug charges in August 2022 ... following a lengthy trial. She was ultimately sent to a penal colony in Mordovia -- where she was forced to work and cut fabric for military members.

In December 2022, though, the U.S. agreed to send Russia convicted arms dealer Viktor Bout in exchange for Griner's release.

Griner told Roberts she dealt with guilt over it all ... saying she felt like she "let everybody down."

But, since touching back down in the States, Griner has become an advocate for those wrongfully detained overseas. She's also expecting her first child with her wife, Cherelle.

As for her hoops career, she's still going strong in the WNBA, getting set to kick off another season with the Phoenix Mercury later this month.