This is what a two game suspension looks like -- Ray Rice delivering a vicious punch to his fiancee's face, knocking her out cold ... and TMZ Sports has the shocking video.

We've already shown you the aftermath outside the elevator ... Rice dragging the unconscious woman on the floor. But we've now obtained video of the punch that put her down, raising the question ... What was the NFL thinking when it wrist-slapped Rice with such feeble punishment?

The incident took place Feb. 15th at the Revel Hotel and Casino in Atlantic City -- after Ray and then-fiancee (now wife) Janay Palmer got into a heated argument on their way into the elevator.

Inside the elevator it's apparent he strikes first ... she hits back ... and then Rice delivers the knockout blow.

The punch knocks Janay off her feet -- and she smashes her head on the elevator hand rail ... knocking her out cold. Ray doesn't seem fazed ... and when the door opens, he drags her out into the hotel.

An employee of the hotel -- which just shut down for good -- tells TMZ Sports he was working there at the time and says the NFL saw the elevator footage before imposing the 2-game suspension.

NFL Commish Something Went Wrong Did His Best

Shameful

FYI -- Ray and Janay FYI -- Ray and Janay got married one month after the attack.

UPDATE -- The NFL says it did NOT see the newly-released elevator footage before it imposed a 2 game suspension on Rice.

This video is a cleaned up version of the raw surveillance elevator video -- the raw is jerky ... so we smoothed it out.