Pain is the means by which you can deter even the strongest attacker.
The human body responds to pain.
It seeks to get away from pain.

Chin na begins with misplacing the bones; a coarse infliction of pain through joint leverage.
The threat of breakage acts as deterrent, whilst actual breakage renders the limbs useless.
But breaking a limb is extreme and vulgar.

Incapacitation is important, but preventing a person from earning their livelihood seems excessive.
A broken bone may cause long-term problems.

More advanced chin na focus upon short-term intense pain, designed to fill the mind with panic.
When an aversive reaction is promoted, the assailant cannot think clearly.
Such pain is also temporary and fades soon after the chin na ceases.