pour vinegar on the wound

Translations
лить уксус на рану
Calling him names after the loss was like pouring vinegar on the wound.
Называть его обидными словами после поражения было как лить уксус на рану.
Definitions
To make a bad situation worse or to intensify someone's pain or discomfort, often by saying or doing something insensitive or hurtful when someone is already suffering.