"It was really uncomfortable, it sucked," Viall tells ET's Lauren Zima. "I mean, I'm all sex positive and all that stuff, but ...you're in a tough spot, right?"
Olympios removed her bikini top on her first group date with Viall during his 2017 Bachelor season, which was recapped on Monday night's The Bachelor: The Greatest Seasons -- Ever! The women were dressed up as brides for a fun photo shoot, with Olympios' portion taking place in a swimming pool, in front of the other women.
"I was literally 10 feet from the rest of the women, they were watching. And I also recognize that Corinne was taking a risk. Whether I agreed with it or not, I didn't want her to feel stupid or vulnerable or judged," Viall reflects. "So, you're really stuck between a rock and a hard place, so to speak. It wasn't my favorite moment."
At the time, Olympios was giddy about seemingly taking things to the next level with Viall, boasting to the camera, "Nick held my boobs today." And despite how uncomfortable Viall was with the moment, he liked Olympios, who made headlines for still having a nanny, gushing about cheese pasta and naps and joking she had a heart of gold and a "platinum vagina."
Olympios ended up making it to the final four, with Viall eliminating her after her hometown date in Miami, Florida.
"I'm proud, in a weird way, I took someone like Corinne far," the Viall Files podcast host tells ET, noting that his final four was filled with strong personalities. "I don't think in other seasons some of those women would have gone as far because I think sometimes, especially The Bachelor, feels like you're being judged. You play it safe, so to speak. I've never played it safe and I think that made for a really good season."
"I actually had pretty good memories [from the show]," he says. "It was a positive season overall and I guess I'm flattered to be in the greatest-of-all-time lineup."
Viall said on Monday's episode that he's single, while Olympios gushed over her boyfriend of nearly one year, Vincent Fratantoni, whom she met on Instagram.
"My life right now is beautiful. I'm so happy," she gushed. "I have an amazing boyfriend and I'm just living life to the fullest. I'm super happy."
The Bachelor: The Greatest Seasons -- Ever! will conclude on Sept. 7 with an episode highlighting Juan Pablo Galavis' season and Clare Crawley's road to becoming the Bachelorette. See more from our interview with Viall on Tuesday's ET.