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

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

What greater wound is there than a false friend?

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

A doubtful friend is worse than a certain enemy. Let a man be one thing or the other, and we then know how to meet him.

Rien n'est si dangereux qu'un ignorant ami; Mieux vaudrait un sage ennemi.

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.

JUDGMENT Be wary of friends — they will betray you more quickly, for they are easily aroused to envy. They also become spoiled and tyrannical. But hire a former enemy and he will be more loyal than a friend, because he has more to prove. In fact, you have more to fear from friends than from enemies. If you have no enemies, find a way to make them.

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

An unsuspected enemy is doubly dangerous.

Your Worst Enemy Could Be Your Best Friend && Your Best Friend Your Worst Enemy

No enemy is so annoying as one who was a friend, or still is a friend,and there are many more of these than one would suspect.

A friend is nothing but a known enemy.

the most dangerous enemy is that which no one fears!