One of the biggest weakness of a libra is that they can’t choose. They never know whose side to take in any decision. Another big problem is that they are perfectionists, who want a perfect relationship as well. A perfect relationship can happen only with a perfect partner and no human is perfect. With this, they become more and more fragile. Another common mistake which mostly all the Libras make is convincing people a lot. They please even them those they don't like.
Another weakness can be that libra is extra kind and helpful. In this regard, people take advantage of them.