万无一失. [wàn wú yì shī]

• no danger of anything going wrong; be on the safe side; ... cannot fail under any circumstances; guarantee complete success; no risk at all; not a chance of an error; (make it more than probable that) nothing will go wrong; perfectly safe; surefire; The chances are a thousand to one, we shall not fail.:

  With him at the helm, we are a hundred percent safe crossing these treacherous rapids.

  由他掌舵， 通过这段激流险滩是万无一失的。