I'm looking for a phrase in German that can equate to the English phrase "Good riddance," a very sarcastic way of saying goodbye to someone/something that you won't actually miss. Is there a way to translate this with the proper negative connotation, or is there really no equivalent phrase? I can't find very much information about phrases like these with "hidden meanings," in a sense, so it'd be great to know if there is a phrase or why one doesn't exist.
As Hagen wrote in a comment, you should use nimmer, which is a old form of nie mehr and niemals. Some dialects still use it nowadays, in others it's only used in fixed expressions as
Auf Nimmerwiedersehen!/Auf Nimmer!
Other common expressions with nimmer:
auf Nimmerwiedersehen weg sein/verschwunden sein
nie und nimmer
an St. Nimmerlein/zum St. Nimmerleinstag
Other than the already mentioned phrases with "nimmer", you could say
Lass' Dich nicht aufhalten.
That translates roughly to "Don't let anything stop/delay you", but has a stronger connotation of "Would you please go already?". The "lass" is a shortened "lasse", the imperative of "(zu-)lassen".