Britney Spears Calls Out Justin Timberlake, Gets Tattoo That 'Sucks'

Britney Spears has clear regrets ... about a tattoo, and about her ex, Justin Timberlake -- she's even posting throwback pics of him -- which can't feel great for her husband, Sam Asghari.

She posted a video of herself getting inked up while in Maui, but never revealed the finished product. As Brit put it, "Can’t show it because it sucks 😂😂😂 !!! Like really really sucks !!! S–t 🙈🙈🙈 !!!”

That's probably exactly what Sam is saying about the Justin pics Brit posted right before her tattoo video. They were throwbacks to JT and Brit in 2001 wearing matching basketball jerseys, and the caption said, "When we used to shoot hoops TOGETHER … that’s when miracles happened."

It wasn't all gushing, though ... she also said, "I came out of my mom’s stomach just like we all did !!! Psss … why always cast me out ??? I’m equal as all !!!"

Brit didn't leave up the cryptic, yet definitely critical, Justin post for too long. That one's been deleted, but she left up the tattoo vid.

As you'll recall, Britney accused Justin last year of using her name to gain serious popularity ... referring to his hit, "Cry Me A River," as a way to blast her publicly for their split.

All the public reminiscing about her ex, can't sit well with Sam ... who was just publicly defending her.

As we reported, eyewitnesses told TMZ Brit was acting "manic" while out to dinner last week -- and video showed her sitting alone at the table and speaking incoherently.

Sam later said his wife was just freaked out by fans taking photos of her, and he denied leaving her in the restaurant. Chivalry at its best.