Lie about you to other people; support other people's lies about you to protect themselves
That is the worst!!!!!!!! I've had that happen.
One of my very best friends is a compulsive liar. I've known that about her since we were in our 20's. I know she lies to protect herself and her kids, but she is the most loyal, generous person I've ever known. We have been very close for over 30 years, and even though she remains a JW, she assures me that she will never abandon me, even if we get disfellowshipped. But, I have to take all the things she tells me with a grain of salt, and try to figure out which thing is really true. I can usually find out through my second son, who is best friends with her second son.
I also had a good friend turn on me because I wouldn't tell her confidential corporate information, from the company we both represented. She had told someone that I knew the scoop and would tell her. I wouldn't. I had been advised by the attorneys and the owner of the company to tell no one (I was involved in a bit of corporate espionage back in 1996............where I uncovered dirt on the head of the company in Malaysia). It was very nasty business, but I kept my mouth shut. Two years ago, they had me sign papers that I would never reveal it. I signed. But my friend would never speak to me again, and hasn't to this day. Some friend.