The battle got so heated, they needed to bring out Diddy as a judge.
The war of words was so incredible, it might even be the best "Drop The Mic" duel to date -- and it wasn't even on TBS, but on "The Late Late Show." (If you didn't know "Drop the Mic" was created by Corden, as it's based on the popular segment on his show.)
Kutcher and the late-night host spit witty rhymes back and forth, tackling topics like Kutcher's movies, Corden's weight, and even took a jab at Kutcher's relationship with his wife, Mila Kunis.
Corden started it off, bringing the heat. "You do great charity work year after year," the host said. "Why don't you save something from dying? Why don't you start with your career?"
Kutcher was ready to hit back, poking fun at Corden's "Carpool Karaoke" and his film "Peter Rabbit."
"People came to see Peter Rabbit battle me, but your battle's with your lady -- her Rabbit's out of batteries," Kutcher quipped back. "My career's been doing fine ever since the 70s, your job's an Uber driver for real celebrities."
"People see me at valet. They say, 'Look, it's a star.' They see you at valet -- they say, 'Dude, where's my car?'"
Corden was calm, cool, and collected, but was ready jab back.
"You made fun of Peter Rabbit and my work on Carpool. I'm not taking that from the tool that made trucker hats cool," he said. "You joined Two and a Half Men when producers had a beef, it's the only time people thought, man I miss Charlie Sheen. You invested all your money in technology and apps. Hell I'd do the same if I knew I couldn't act."
Kutcher wasn't letting these jabs getting him down and hit back by saying that Corden looked like a "hard-boiled egg applying for a loan."
"I hate to kick a man when he's down in a slump, but I'm looking at the baby of Kim Jong-un and Donald Trump," Kutcher continued.
"You married Mila and I guess that's cool, but why the hell is she still with the loser she dated in high school?" Corden rapped back.
Kutcher came back with jabs about "Ocean's 8" and Corden's weight.
"You did Ocean's 8 that’s worth mentioning, probably should have called it Ocean's ate everything...and before that you did so many animated flicks, that we haven't seen this face in a movie since we last saw your d--k."
Since this was, like we said, one of the most heated "Drop the Mic" battles in history, they needed a proper judge to choose the winner. Who would be better than Diddy?
"The Four" judge walked out and chose the winner.
"In one of the closest battles in the 'Late, Late Show' history." Diddy said. "The winner -- by only a half a point -- for the very first time in history, James Corden!"
Watch the full battle below.