Gangster.

Yeah, we know ... scripted ... but still -- murder?? Wow.

Here's the deal, Becky came out to the ring after Rousey destroyed Bayley in a match on 'Monday Night Raw' -- and challenged Ronda to a title fight at Wrestlemania.

That's when Ronda -- the former UFC women's champ -- grabbed the mic and spat out some homicidal trash talk.

"You, me and everyone else here knows that I could re-break your face faster than you can say, 'Nia Jax,'" Ronda said.

She continued ... "You, me and everyone else here knows that I have the ability to kill you with my bare hands without even breaking a sweat."

"And, the only thing stopping me is my decision not to!"

Rousey also bragged about being a household name for a decade while Lynch was still earning her stripes.

Then came the final threat ...

"You gotta learn something here honey -- any ring I step into is mine. I own the ground under my feet and I'm gonna own you at Wrestlemania."

The craziest thing about Ronda's night is the way she recovered from her awkward 2-minute rant before the match ... where she seemed legitimately rattled by the pro-Becky crowd.