Not a German but Duden disagrees with you [0]: "etwas in der Absicht, es zu verbessern, schlechter machen".

[0]: https://www.duden.de/rechtschreibung/verschlimmbessern

German here, this is the right definition, trying to improve something but ending up making it worse.

that's not disagreeing at all (american partial german, partial pole)

It is a different meaning from that in the parent comment by OroPla.