When they believed it might have turned good it obviously hadn't.
It was the birth of a star and realized that the Daleks could not destroy all non-dalek life, that the Daleks would ultimitely lose therefore he was on the losing side. So he changed sides.
Then in the end the Dalek is converted through what amounts to a religious experience of encountering hatred so pure and beautiful (to he Dalek) that he converted to that hatred, forsaking his native hatred.
There was no real attempt to turn the Dalek good at all. Morality was never a relevant issue, yet it dominated the context.
Oh, I see what you were talking about. There was still an attempt to turn it good. That was the point of the Doctor showing the Dalek his own consciousness. It just didn't turn out the way he wanted. Just because the attempt failed, doesn't mean it wasn't there. Morality is still a relevant issue. The Doctor wanted to make a morally good Dalek but failed because of his own moral failings.
I may have to rewatch that part, because it came across to me as if they were trying to return it to the state it was when the radiation affected it, and the doctor was sad that it revealed the worst in him, and not the best. I may have missed something.
They were definitely trying to return it to the state it was at because of the radiation. The radiation allowed the Dalek to expand its consciousness beyond its normal parameters and gain a respect for life. They wanted the Dalek to remember what it felt and what it learned during that time and keep it. The radiation leak proved that a Dalek was capable of change. It's just really freakin hard. For a Dalek to gain a respect for life without being injected or spliced with magical human DNA is a pretty big breakthrough.