TMZ Live

It's bad enough rapper YC fiancee busted him with a Vegas bartender the night before their wedding -- but now instead of apologizing ... he's blaming the whole thing on the drink-slinger.

Yung Chris was on TMZ Live on Monday when he described the encounter with the bartender -- he claims she got flirtier with every drink she brought, and every $100 tip he gave her. Funny how that happens.

But rather than do a mea culpa ... YC admitted he was down to give her more than a tip. As he put it, "It's the night before (my wedding) so whatever happens now they ain't gonna hold it against me."

His fiancee, Tia Anderson, disagreed ... strongly ... and pulled the plug. You gotta hear him explain how the bartender ratted him out -- and why Tia "still has an attitude" about his cheating.

Dee Snider just unleashed a bitter rant about Twisted Sister drummer A.J. Pero's death -- saying his heart attack was totally avoidable, but Pero did nothing to save himself or protect his family.

Dee came on TMZ Live to talk about the band's upcoming farewell tour, but ended up venting about Pero. Dee told us he's in the anger stage of grieving because ... he says Pero knew he had a history of heart disease in his family, but never got checked out.

A.J.'s autopsy results -- which Dee revealed -- are what really set him off about his friend's death.