This wild scene unfolded Sunday night at the Laugh Factory here in Los Angeles -- where Donnell went up to do a set ... and Corey went on after him when we're told he started hurling wild claims and barbs at Donnell and Dave Chappelle's expense.

Donnell tells TMZ he wasn't going to let Corey torch his close friend -- the two of them were on "Chappelle's Show" together back in the day -- so he confronted him over it.

That argument is what you see here on video, obtained by TMZ, with Donnell going absolutely ballistic on Corey -- whom you can hear calling DR "mild" and a lame funny man.

You can also hear Corey questioning Donnell's street cred ... and Donnell was ready to defend himself and his rep -- which he did from the audience level, right in front of everybody. Indeed, it must've been pretty surreal to see play out live.

Now, Donnell claims another inflammatory comment that Corey made played into how angry he got -- namely, Corey allegedly saying that anyone in comedy who has 3 movies or more under their belt has had to perform fellatio on someone in the biz.

The reason Donnell says he got as fired up -- in addition to feeling insulted and hearing his friends get insulted -- is because he has 3 movies, and he insists he's never done anything like that in his career.

BTW, this beef between Donnell, Corey and Dave runs pretty deep -- Corey recently did a podcast where he trashed DC ... and suggested he simply wasn't funny, let alone a legend.

In terms of how this ended, Donnell tells us he ended up walking away from the situation before things escalated further. However, he says he'd still like to hash things out with Corey in a more calm setting and hopefully put their differences aside.