Lamont Richmond is the guy with whom Biebs picked the fight.

We’re told this is how Lamont’s story goes … he’d just left a bar when he saw Justin outside the Westin in Cleveland.

Lamont says he and his 2 chick friends chilled with Bieber for a short time.

Lamont says he dared to ask Bieber if the women could take a pic and get a John Hancock.

Lamont says Justin reeked of alcohol and got all Quien Es Mas Macho on him, “Puffing his chest up,” and then took a swing.

You see Lamont restrain Bieber in the video … and says he’s sure, if he went full force, he would have killed him.

We’re told Lamont has already met with a lawyer and plans to sue.

Justin Bieber