The Uttarakanda is the most controversial book, as it contains the story of Rama banishing Sita from Ayodhya, and of his beheading a shudra named Shambuka for performing religious worship not appropriate for his varna. To many, both these actions seem to detract from Rama's reputation as a model of ideal conduct: when he banished Sita in spite of her innocence, merely because the people were gossiping, he is said to have preferred falsehood to truth; and by attacking Shambuka in a state of helplessness (i.e. while he was meditating), Rama violated the Kshatriya code of honour.
Significantly, these episodes are not found in any early version of Rama story. The Mahabharata, the Harivamsha, and the Vayu, Brahmanda, Kurma, Garuda and Vishnu Puranas all give more or less detailed versions of the story, but none of them mention either the banishment of Sita, or the slaying of Shambuka. Some consider the entire Uttara Kanda to be an addition, not written by Valmiki.