A false friend is more dangerous than an open enemy

One fake friend can do more harm than 10 enemies... Be smart choosing your friends.

An injured friend is the bitterest of foes.

Today I know this: when it comes time to take stock, the most painful wound is that of broken friendships; and there is nothing more foolish than to sacrifice a friendship to politics.

A foolish friend may cause more woe
Than could, indeed, the wisest foe.

An insincere and evil friend is more to be feared than a wild beast; a wild beast may wound your body, but an evil friend will wound your mind.

Our true friends are those who are with us when the good things happen. They cheer us on and are pleased by our triumphs. False friends only appear at difficult times, with their sad, supportive faces, when, in fact, our suffering is serving to console them for their miserable lives.

One enemy can do more hurt than ten friends can do good.

Unreal friendship may turn to real
But real friendship, once ended, cannot be mended

There is a stranger who is more than a friend, and a friend who is worse than a stranger.

The worst solitute is to be destitute of true friendship.

A friend is nothing but a known enemy.

It is more shameful to distrust one's friends than to be deceived by them

Nothing is as dangerous as an ignorant friend; a wise enemy is to be preferred.