The first officer to taser Kevin Spratt at a Perth watchhouse concedes he used the weapon to force the Aboriginal man to obey his orders, a corruption hearing has heard. ... [LINK]
Clearly, using severe pain to force (verb) or coerce someone to do something meets the exact internationally-agreed definition of "Torture".
Notice that "lawful force" is a noun.
Using severe pain to "force" (the verb) someone to obey you is Torture.