You can write character on following points
1)famous innovator
2)remarkable person despite his high status
3)extremely kind and modest
4)encourage Helen and miss Sullivan
5)explain many of his experiment to Helen
6)fond of children s but never happy when a deaf child comes in his arm.
7)work lot for deaf
8)in short he was really a great man devoted to his field but at same time he was great human being who is very modest. Helen pay glowing tribute to him