Thanks for A2A @Anirudh Singh (अनिरुद्ध). According to me, Kaikayi, second wife of King Dashrath.

• As a young girl and only sister of seven brothers, Kaikeyi grew up without a maternal influence in her childhood home. Her father had banished her mother from Kekaya after realizing that his wife's nature was not conducive to a happy family life.
• Since her position depended on Kaikeyi's status at Court, Manthara lost no opportunity to feed young Kaikeyi's insecurity and jealousy of Kausalya, despite Dasharatha's obvious enchantment and love for all of his wives.
• Also, she was very fond of Rama. It was Manthara, who instigated her against him.
• Bharata contests her views vociferously and despises her for her act of banishing the rightful heir Rama to forests as if punishing him for no fault of his. Therefore, his son hated her.
• King Dasharath tries to reason with her in terms of internal security of the kingdom, people's will, the Court's decision to crown Rama; none of which seems reasonable to her.
• Kaikeyi demanded that Bharata be crowned king and Rama be sent to the forest for fourteen years. Hearing this, Dasharatha fell into a swoon and passed the night in a pitiable condition in Kaikeyi's palace.
• Bharata blamed her for his father's death and swore never to address her as Mother again.
• He also cursed her saying that no father shall hereafter name his daughter Kaikeyi. Realising her mistake, Kaikeyi repented sending her most beloved son away for 14 years.