Wikimedia Bugzilla is closed!

There is currently no way to remove an accidentally saved wrong or invalid translation.
Existing options:
- make is a valid translation
- copy the original and make it fuzzy

Yet, you may not always be able to find a correct translation, e.g. when lacking information or feedback from support questions that you cannot have at once, or you just may have no more time to deal with a lengthy and complex message adequately.

Latest, when we have user defined fallback chains, copying the original becomes at least a questionable choice.

If possible vandalism is of concern, we may restrict deletion to ones own translations, and/or maybe even to some time after saving, since most often, you instantly know that you just hit the wrong button. I pledge for no restrictions until their necessity creeped up in reality  ;-) while having an rights "Delete translated message" / "Delete translated page element" that we may use if needed.