Have the Opposite Effect Than Intended on a Plan
This page is the CodyCross answer for the clue below from Greece, Group 666, Puzzle 2 (Spartan Army).
Question is: Have the Opposite Effect Than Intended on a Plan
and the answer is: BACKFIRE
Word Meaning:
BACKFIRE — A premature explosion in the cylinder of a gas or oil engine during the exhaust or the compression stroke, tending to drive the piston in the wrong direction.
Definitions from Wiktionary.