disimprovement

Reduction from a better to a worse state.

[...] '[T]is very reaſonable, that all ſhould be obliged to the Law of Justice. [...] And as to the Public, 'twould be all one as if there were no Property; and then for want of Encouragement and Security, the final iſſue of the matter would be, an utter neglect and diſimprovement of the Earth, and a continual diſturbance of the Public Peace.

From day to day the intelligent student can watch the course of the affection before him, notice the finest shades of improvement or disimprovement, test the results of treatment, and verify for himself the truth of both diagnosis and prognosis.

Attempt to make something better while ending up worse than before.