1) The main character is the ugly duckling. There were conflicts between him and the ducklings, the march birds' mother and the mother duckling. They all were criticising him of his ugliness.
2) The major problem is that everyone felt that the ugly duckling was very "ugly" and thus no one wanted to play with him. Therefore he felt very sorry for himself and could not stop crying.
3) The other characters all prejudiced him and did not want to play with him.