Ma sita was mericiful as a mother would be to her children .
Even though she was capable of burning Ravan to ashes . She refused to do it as she wanted Rama to gain all the fame .
O Dashagriva! You deserve to be burnt down. Yet, I am not burning you down with my energy. I belong to the intelligent Rama and you are incapable of abducting me. There is no doubt that this has been ordained by destiny for the sake of you being killed.
Hanuman wanted to kill the remaining female rakhsasas who tormented her with their antics but Sita stopped him killing them
You are devoted to your husband and when you were in Ashokavana, they oppressed you. These rakshasis are extremely terrible and they are horrible in speech. Grant me this boon. I wish to kill them, using different kinds of blows. O beautiful one! I will strike them and bring them down with fists, hands, feet, teeth and terrible blows with the thighs. I will eat up their noses and ears. I will pull out their hair. When I strike, kill and make them suffer, their mouths will turn extremely dry
(6–101)
She was very merciful to everyone