regress
re-gress
verb
To return to a previous, less developed, or worse state or condition.
"His behaviour started to regress after the incident."
Thesaurus
Synonyms: retrogression, reversion, retroversion, regression, retrovert, return, turn back, revert, reasoning backward, recidivate, relapse, fall back
Antonyms: advance, come along, come on, get along, get on, progress, shape up