"Dalek" perfectly showcases the fury of the Doctor. His rage at his terrible role in ending the Time War and his guilt at his own survival are perfectly portrayed by Eccleston when the Doctor comes face to face with a Dalek, who he had thought long destroyed along with the Time Lords. Eccleston's acting is at its finest when he faces down the Dalek, his barrage of "Fantastic!"s ranging across every emotion from relief (when it fails to kill him) to wonder to quiet hatred, which explodes into a raging rant that holds all the deep-seated contempt and loathing he feels towards his worst enemies. It's this line that sticks with me
"The Daleks have failed! Now why don't you finish the job, and make the Daleks extinct?! Rid the universe of your filth! Why don't you just DIE?!"
The Dalek's response, "You would make a good Dalek," sends chills down the Doctor's spine, as he once again has to question how far he is willing to go before he turns into something he hates. The sense of what it means to be alien or human is an excellent theme well explored here as both sides give into their opposite worldview as the Doctor is consumed by hatred and the Dalek is humanized by Rose's DNA. It's utterly fascinating watching these two paradoxical creatures, the last of their kind (allegedly) react to that very fact. Fantastic Quotes From The Doctor: "Release me if you want to live." Doctor: "Let me tell you something, Van Statten. Mankind goes into space to explore, to be part of something greater." Van Statten: "Exactly! I wanted to touch the stars!" Doctor: "You just want to drag the stars down and stick them underground beneath tons of sand and dirt and label them! You're about as far from the stars as you can get."