6. His Relationship With The Ood
One of the greatest plots that Ten has given us is the relationship between Time Lord and Oodkind. The Doctor's interest and affection for the Ood is evident from their first appearance in "The Impossible Planet," and their importance in his own timeline gains momentum until their dreams prophesy the return of the Master. The Ood and the Doctor are an incredible pairing. Where the Doctor has two hearts, the Ood have two brains a perfect mirror and compliment for each other. In trying to and succeeding in saving them and their planet from slavery, Ten reveals his compassion not only for humans, but for all races and peoples in the universe.