disimprove

verb3

1. •
   (rare) To make worse.

   • To which may be added this advantage, that the services of churchmen are rewardable upon the church's stock: no need to disimprove the royal banks to pay thanks to bishops. — 1642
2. •
   (rare) To deteriorate.
3. •
   (informal, rare) To try to make something better but end up making it worse.