Blac Chyna -- Disses Tyga ... Promises New Boxer BF Crazy Sex

More venom from Blac Chyna ... who went out of her way to diss her baby daddy, Tyga, Tuesday night -- and to twist the knife, she bragged about the insane sex she plans to have with her new boxer BF.

Chyna was leaving 1 OAK nightclub in Hollywood when she told us she has BIG BANGIN' PLANS to break J'Leon Love's pre-fight vow of abstinence once the final bell rings on June 20th.

"It's over for him!" Chyna bragged.

That's when the topic turned to Tyga -- and Chyna fired off a few shots in his direction.

Those two have been beefin' ever since they broke up back in August ... and it doesn't seem like it's ending anytime soon.