Synonyms for Once and for all:

• adj.

  •last (adjective)
  • outer most,
  • aftermost,
  • endwise,
  • lattermost,
  • least,
  • far off,
  • uttermost,
  • Ender,
  • rearmost.
  •lattermost (adjective)
  • latter most,
  • end most,
  • more hindermost,
  • latter-most,
  • most hindermost,
  • end-most.

• adv.

  •finally (adverb)
  • at long last,
  • it's about time,
  • in the end,
  • inexorably,
  • in conclusion,
  • irrevocably,
  • at last,
  • at the end,
  • sooner or later,
  • after all.

• adv

  •finally (adverb)
  • enduringly,
  • for good,
  • Determinately,
  • inescapably,
  • decisively,
  • beyond recall,
  • past regret,
  • convincingly,
  • once for all,
  • done with,
  • for ever,
  • with conviction,
  • for all time,
  • beyond shadow of doubt.

• n.

  •
  • unalterably.
  •conclusively (noun)
  • conclusively.

• Other synonyms:

  •
  • finally.
  •Other relevant words:
  • one time,
  • on one occasion,
  • for the nonce,
  • pro hac vice,
  • once.

Antonyms for Once and for all:

• adv.

  • Other antonyms:
    inconclusively.