overpotent

adjective

over·​po·​tent ˌō-vər-ˈpō-tᵊnt 

: excessively potent

… he was given quantities of belladonna, probably an excellent remedy, but one which proved overpotent in the case of Dr. Marston's delicate and sensitive little boy.

—William Sharp

Word History

First Known Use

1593, in the meaning defined above