When Rama rejected her telling her that he was already married to Sita, she became furious and thought that Sita was the real obstacle. In her anger, she resumed her rakshasa face and tried to attack Sita. To protect Sita, Lakshmana at once took up his sword and maimed Soorpanakha by cutting off her nose and ears.
Disgraced and mutilated, Soorpanakha uttered a loud wail and disappeared into the forest. Bleeding and mad with pain and rage, she flung herself on the ground before her brother Khara and narrated to him what happened.
Khara sent an army with her to kill Rama and Lakshmana, but the army was annihilated. Then Khara himself went with his brother Dooshana and a great army; but once again Rama utterly destroyed them and came out victorious. The Devas showered flowers from on high and cried in joy.
How did Rama destroy such powerful rakshasaas and a whole army single-handed? The answer is that when God assumes human form and is engaged in fulfilling His promise to save the helpless, His limitless power comes into play!