St. John of Damascus gives the Orthodox definition of evil:
For evil is nothing else than absence of goodness,
just as darkness also is absence of light.
( Exact Exposition of the Orthodox Faith, Kindle Loc. 735-36)
So, if you want to overcome evil, do good for you will bring goodness to any situation. Goodness will no longer be absent. Evil will be overcome. If you find yourself in the face of evil, do the good so that goodness will be a presence. Then one will not be far from God.
[I do realize there is an oversimplification here. Terrorists, violent criminals, abusers of all kinds will not be changed in any one second or one instance by a brush with goodness and might even mock the goodness before trying to destroy the good. So one does have to have the wisdom to know when it is time to flee or fight or as Kenny Rogers sings it: “You’ve got to know when to hold ’em, Know when to fold ’em, Know when to walk away And know when to run.” But there are many occasions in life where we could make things better by doing a good thing, making goodness present, choosing the next right thing, lighting a candle instead of cursing the darkness. And especially spiritually, we can come to realize our fear of Satan is misplaced for Satan is ultimately an absence, not a presence. Doing the good is enough to prevent Satan from entering our hearts or minds, for the goodness is real in a way that Satan is not.]