The procedure I use when a card gets flagged, in order:
Ask whether I actually need this. Honestly. A lot of cards were added in an enthusiastic first month and correspond to nothing I care about now. If the answer is no, delete it and feel nothing - see below.
Suspend it and come back. Sometimes the problem is that it depends on something else I have not learned yet. Suspending and re-enabling later works surprisingly often.
Rewrite it. Split it if it has multiple parts. Add a clue that disambiguates. Add context: where it comes from, what it relates to, a mnemonic, an image. Turn a recognition card into a production one.
Learn the underlying thing properly, away from the deck, then rewrite the card.
Then delete, if none of that helped.
One caution: rewriting resets its history, which is correct: it is a new card and its old failures were the old card's fault.
And a preventative note for new cards: the single most useful rule is one fact per card, phrased so there is exactly one correct answer. Most leeches are created at the moment of writing, not discovered later.