When you read the poem the first time you become sympathised with the knight. As things are mentioned in the poem you do not entirely understand for example I see a lily on thy brow. When you read into it you realise this mean he is depressed. But when he meets this lady he gets happier. But at the end he has a dream in which the people say la belle dame sans merci and he thinks he is one of the long line of people who have been used by the femme fatale or fatal woman.
But when you read it a few times more and read each line carefully you realise some things. The things you realise tend to balance out your view on which character seems to receive the most sympathy. Firstly in this poem she has no voice. This in turn means that she cannot express herself like the mean expresses himself and his sadness. She cannot defend herself, as she has no voice. Because of this you can have many of your own interpretations of the woman in the poem. The woman in this poem seems almost to have a supernatural presence. Some things in the poem suggest this for example the first few lines describing her describe her as a faerys child.
Even her appearance seems to be supernatural. He describes her as having wild eyes. As she is seen as supernatural the readers would have less sympathy with her, as she may not seem human. Some things when first read might me misinterpreted or might have more than one interpretation. For example it says And made sweet moan. This could mean that she is moaning in pleasure or it could also mean she is moaning in a bad way as in she is unhappy. Thats why the first time you read the poem you do not fully understand the poem and you cannot understand the womans feelings and therefore will not be given a chance to sympathise with the women. At the end of the poem the man has a dream and when he wakes up and the women is gone. This part makes us sympathise with the man because we think the woman without mercy has used him.
At the end of the poem he is as sad as he was in the beginning. And the dull surroundings have returned, Though the sedge has witherd from the lake. He seems to be alone and loitering in the end as he was in the beginning. But I dont think it is totally the womans fault because he was a passive victim and he followed her as she led him. We may think that he is a victim of a supernatural person as she is often described like this. But when you think about it she hasnt committed a crime. She did make him happy even if she it for a while and you cannot tell that she was happy herself. She seemed to lead him instead of the other way round She took me to her elfin grot overall I dont think the writer creates sympathy for only one person but for both but it depends on how you view the poem.