And he wasn't the only one to find the tattoo amusing.
Said user @RafiDAngelo: "Next time you're feeling sad, remember that you're not Ben Affleck so you (probably) don't have a tattoo so big and so ugly and so universally ridiculed that you had to lie and say it was only temporary and just for a movie when it is so clearly not."
And @dashiell wrote: "Ben Affleck's back tattoo is, and I'm saying this without hyperbole, one of the funniest god***n things I've ever seen in my entire life. Holy moly. What a wonderful gift to all of us this is. Truly a great day to be alive because of this obscenely dumb tattoo."
But while the inking was roundly ridiculed, others were simply happy to enjoy the photos of the 45-year-old.
"Batman's got a sweet dad bod," wrote @hyacinthgrrl.
While it's now pretty clear that Affleck's ink is here to stay, the Argo star attempted to downplay it when he was asked about it two years ago.
At that time, he dubbed the elaborate inking as "fake for a movie" while speaking with Extra.
"I actually do have a number of tattoos, but I try to have them in places where you don't have to do a lot of cover up," he said. "They get sort of addictive, tattoos, after awhile."
But there had been clues that the tattoo might be the real deal.
Despite Ben's protests, his two most prominent exes - Jennifer Garner and Jennifer Lopez - made it clear they disapproved when they were asked about the inking.
Garner told Vanity Fair in 2016 that she took exception to the possible inference that Ben was "a phoenix rising from the ashes" emerging from their June 2015 split.
"Am I the ashes in this scenario?" she said. "I take umbrage I refuse to be the ashes."
Lopez called her Gigli co-star's tattoo "awful" as she appeared on Bravo's Watch What Happens Live in February 2016.
"It's awful! What are you doing?" she said. "His tattoos always have too many colors, they shouldn't be so colorful. They should be cooler."
Affleck's inking was revealed on the beach in Honolulu, Hawaii as he filmed new Netflix movie Triple Frontier with actors Charlie Hunnam, Garrett Hedlund and Oscar Isaac.