Natan Levy says his recent beatdown of an internet troll could have been much, much more violent ... but he tells TMZ Sports he let his foot off the gas just a little bit so the guy still had "some brain left to take the lesson in."
The UFC fighter, who's Jewish, sparred the smack-talking social media user, Ben, a few days ago ... after the guy defended noted antisemite Nick Fuentes in an exchange on X.
Ben met up with Levy at his gym in Las Vegas .