Bad friends are best avoided completely, and you should be wary when you meet new people. Always make sure that you clearly understand the motivation of the other person before you form a bond of close friendship. Some people will try to make friends with you because they covet what you have. Others may seem nice but they may not be capable of true loyalty or legitimate closeness. A bad friend can cause devastation on a scale that even your enemies may not manage, because they are closer and know more of your secrets.
When a toxic person can no longer control you, they will try to control how others see you. The misinformation will feel unfair, but stay above it, trusting that other people will eventually see the truth just like you did.