"Seinfeld" star Michael Richards allegedly unleashed a devastating ass kicking on a photographer in L.A. last month ... this according to a new lawsuit obtained by TMZ.
According to the suit, photographer Brendon O'Neal claims Richards approached him on an L.A. street on August 25 in a "menacing manner ... with closed fists" -- then proceed to beat the crap out of him.
In the suit, filed Friday in L.A. County Superior Court, O'Neal claims Richards punched him in the face, knocked him to the ground, and then "proceeded to kick [O'Neal] numerous times, directing the blows to [O'Neal's] arms, hands, and camera."
According to the suit, O'Neal claims he suffered "great mental, physical, and nervous pain and suffering" -- and is suing for an unspecified amount for damages, medical expenses, and much more.
The lawsuit gives no explanation as to what triggered the alleged beating.
Richards has been known to go off ... e.g., the famous "N" word rant at The Laugh Factory in 2006.
Calls to Richards' rep have not been returned.