More Severe Than the Three Chamuros:

The Chida zt'l (Sefer Lev Dovid) quotes Sefer Birchas Tov as saying that lashon hara is the very worst aveirah. It is even more severe than the three cardinal sins of idol worship, immoral relationships and murder. Therefore, the current golus, which was caused by lashon hara, is longer and more difficult than the previous golus, which was caused by those three sins. He adds that the only way to rectify this is through Torah study. Rav Shaul Katzin zt"l, one of the Gedolim of Yerushalaim, was very careful with his words. It is related that he once was sitting in his home and speaking to a close friend of his, when the man began to speak disparagingly about someone else. Rav Shaul immediately screamed at him, "Get out of my house! I can't listen to this!" The man left in shame. A few days later, when they met again, Rav Shaul said, "Don't think that I hate you now. On the contrary, the reason I yelled at you is because I love you so much and wanted to save you from a very severe sin!"