A cheetah can’t kill an adult human that defends himself defiantly because they are not built for power. Cheetahs are not as agile as lions and leopards and do not have sharp claws like other big cats. They have much smaller mouths and a much weaker bite force. A cheetah could only kill a defiant human if it grasps hold of their neck and the human does not punch or kick it forcefully. Moreover, it would have to be voluntary suffocation and submission to the cheetah.