Boxing champ Claressa Shields -- a 2-time Olympic gold medalist -- says UFC star Amanda Nunes would get a RUDE AWAKENING if they ever fought ... explaining, "I T-Rex bitches!"
23-year-old Shields is the biggest star in women's boxing right now -- she's the undisputed, unified champ in TWO weight classes with an 8-0 pro record. She's a BEAST!!!
She's also very close with Cris Cyborg -- and was at UFC 232 back in December when Cyborg got knocked out by Nunes.