The Doctor: The Daleks have failed! So finish the job, make the Daleks extinct. Rid the universe of your filth. Why don't you just die? Dalek: You would make a good Dalek.
Nine had a great deal of great moments with the Daleks, so here's another one - one so poignant that it's even had been called back to in Series 8, where Twelve was referred to as a "good Dalek". This moment once again showcases the sheer amount of loathing that the Ninth Doctor shows for the deadly pepperpots, He's urging the Dalek to destroy itself with a sense of desperation, to the point that he loses control as the speech ends, yelling the last bit with all the venom he can muster. The Dalek almost steals it with one of the best comebacks in the history of the show. It's clear how horrified and worried the Doctor is after it's suggested by one of his mortal enemies that he "would make a good Dalek", that he embodies what he has come to despise and might be as destructive as any Dalek could ever be. It also hints at a darker aspect of the Ninth Doctor - which is why it's really his moment - and suggests that the production team aren't scared to go into the less savoury aspects of the character. It makes Nine more complex and adds a lot of depth to what is arguably the best episode of the series. Eccleston is again on form, showing all the Doctor's stone cold fear and horror at the end of the exchange with just a look.