Overstate, exaggerate.
overstate, magnify
understate, mute, tone down, subdue
The antonym of "inflate" is "deflate", if used to mean 'fill with air'. If 'inflate' is used as a meaning of 'exaggerate', then the antonym would be 'understate'.
what is an antonym for exaggerate? Understate is the most correct one, and sometimes people say, "He's just being modest," or "don't be modest," to say that he was not exaggerating.
To say that the Grand Canyon is nice is to understate its grandeur.
The opposite would be to degrade, lessen, diminish, decrease, or reduce.
overstate
Minimize? Belittle?
yes
Unethical and illegal.
Depreciate, minimize or understate.
Downplaying the significance of an event or emotion.