The Game is going HAM on a guy who used to be tight with Chris Brown -- accusing him of masterminding the attack on Game's car and Chris' house ... but the guy's firing back.
Game pumped up the beef by calling out Wackstar -- a former CB posse member -- and saying, "Tell these fans who really had Chris brown auntie tied up & his house broke in you pu**y ass fa***t."
Homophobic slurs aside, Game also made a clear threat -- "When I see you I'm gone break yo f**kin jaw...So have yo gun on you pu**sy."
Wackstar seems unfazed by the accusations on Instagram. He called Game a fake gangsta, saying ... "I know the real you, you wouldn't hurt a f**kin fly." For good measure, he added ... "#ChangeOfHeartAssN**a" ... a shot at Game's past appearance on the TV game show.