Man Pulls Massive Knife Out in Heated Confrontation at L.A. Wendy's on Video

Things got seriously scary at a Wendy's in Los Angeles ... when a man pulled a giant knife on another guy during an altercation and threatened to kill him ... and it's all on video.

Ya gotta see the footage ... two men get in each other's faces at the Northridge fast food restaurant when one guy pulls a knife. The guy in the baseball hat dares the knife-wielding man to touch him and asks if he's going to do some stabbing.

The armed man responds ... "I'll f***ing kill you, dog."

From the looks of it, the whole thing started when the guy in the baseball cap came up to the man, who was sitting at a table eating with a woman.

The guy in the cap came up to their table, seemingly antagonizing the pair when the guy got up from his seat and pulled the massive knife out from behind him.

The men were swearing and throwing chairs before taking the fight outside. That's when the cops pulled up and cuffed the man with the knife.

Witness Jesus Lepit told KTLA the guy in the baseball hat was the instigator, saying ... "The customer was still talking to the employees, arguing with them."

Lepit said the couple was "minding their own business" when the guy in the hat approached them and got in their space.