The love that Sydney Carton feels changes him to be someone that he isn't, just like the hatred that Madame Defarge has in her heart changes her to become a much eviler side of herself. The love that Sydney feels for Lucie is so strong and unselfish and undieing that he gives up his life just so she can be with the man she loves, and he does this in such a way that she doesn't even know what he's done for her until they are back in England, and long after Sydney has met Charles's fate. Sydney's love is the most unselfish love there is and for what he did, Lucie named her son after him. Now, where Sydney is a symbol of pure love, Madame Defarge is one of pure hatred. Her hatred, though not undeserving, clouded her vision and thus lead her to her demise at the hands of Miss Pross.