Answer: undoer

AnswerCrossword Clue
UNDOERCause for a downfall
UNDOERDestroyer
UNDOERLace loosener
UNDOERWrecker of plans.
UNDOERRuinous one
UNDOERDisassembler
UNDOEROne taking back an action in MS Word, say
undoerone who undoes (to bring to ruin)
undoerdisturb the composure of upset she's come undone
undoerduce 3
undoercome open or apart
undoermake of no effect or as if not done make null reverse
undoerruin the worldly means, reputation, or hopes of a politician undone by scandal
undoerto open or loose by releasing a fastening