weaken

Synonyms: abate adulterate break up cripple crumble cut debase debilitate decline decrease depress devitalize dilute diminish droop dwindle ease up enervate exhaust fade fail faint flag give way halt impair impoverish invalidate languish lessen limp lose lose spirit lower minimize mitigate moderate reduce relapse relax sap slow down soften temper thin thin out tire totter tremble undermine vitiate wane water down wilt

Antonyms: build up strengthen