Wait for it to sleep find some of it's shit slather it on, sneak up on it and hope I can cripple it by cutting through a tendon. Run like hell, repeat on other leg when it calms down. Hope it can't eat and dies before time runs out. Not sure I risk getting near it's head crippled or not.
I don't know if I could cripple it, but for $500mil I'd give my strategy a shot.