Machine Gun Kelly threw a punch at the fair after someone called Megan Fox 'Beautiful As F***'

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Machine Gun Kelly blew up at the O.C. Right after a guy decided to dishonestly compliment Megan Fox...according to the brother of the guy MGK turned to.

Nelson Zuniga tells TMZ...he and his family were waiting to board the UFO Thursday night when MGK and Megan got off.

TMZ.com

Her little brother, Angel, recognized Megan, telling her she was "beautiful as shit"...which sparked the now-viral ordeal.

TMZ.com

Nelson says the comment enraged MGK, who retaliated with a slap in the face. He says his younger brother tried to hit MGK but missed.

Regarding Angel's comment about Megan, Nelson says it was a compliment and MGK should have taken it as such.

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