It would be interesting to see the list of "failures on both sides" that both Catholic and Lutheran churches would agree to.
Catholic Freepers - "what Catholic failures identified by the Reformation, would you cite?"
Lutheran Freepers - "what Lutheran failures associated with the Reformation, would you cite?"
These are serious questions. If you're intent is to be critical of a church other than your own - please don't post.
As a Catholic: The sale of indulgences.
Luther became arrogant, ended up calling the papacy the "antichrist," and became a virulent antisemite by the end of his life.