Disclaimer: I do not own Doctor Who therefore while the situations described are all my own as is the unique wording, the characters (etc.) are property of BBC.
This story is intended to cover any regeneration you want, though one portion does specifically pertain to 9. GEN.
Redeeming Qualities
The human capacity for love amazed the Doctor. It always had.
Sometimes, when things were particularly bad and he wanted nothing more than to forget the troublesome little blue-green world, it was the only thing that kept him coming back.
He thought of abandoning the humans to their fates when he happened to pass a newspaper and saw stories of mass murder and mayhem and he wondered why, why did he continue to come here when all it ever showed him was how truly terrible human beings could be to one another? He thought of never returning every time he watched as an older child picked on a smaller one. When he passed animal shelters and heard the poor beings inside calling out so desperately to be loved by someone, anyone, because their previous masters had not, the Doctor thought maybe he hated humans a little. When they finally invented a communal place to talk from anywhere on the planet and immediately used it to torment others, he lost a little more faith and once again wondered if he should just stop hoping for more from the stupid apes. There were many times in his visits that he thought, "This is it. I'm never coming back. The Gilese system has some lovely people… maybe one of them would want to go travelling."
But, every single time something stopped him. His various companions never really asked, and he never told, but the Doctor had visited Earth many (many many) times on his own. What could he say? He liked the tea and Earl Grey never seemed to taste as good leaning against the TARDIS consol as it did sitting in a little coffee shop and watching an oblivious world go by. When he finished his tea, he would wander the city (whatever city he happened to be in) hoping to find some small adventure (or big adventure, he really wasn't picky).
On these adventures and wanderings he saw many things. But the most important was this; humans loved. They loved so powerfully; with all their heart and soul thrown into the action in the sort of reckless abandon he delighted in. But, they were shy about their love. They made it difficult for an outsider like himself to find. They showed the world all of their hatred and fear of that which was different from themselves, but hid their love away in the small corner of their heart where it could only cause them pain. But, the Doctor was practiced in seeing the secret and he knew humans better than they knew themselves.
Often, he remembers the first time he was lifted from despair about the race he had taken under his wing….
It's his ninth incarnation and he is angry. So angry. At times he wants to scream and rage and just stop. For the first time he feels old, even though by his people's standards he really isn't. His people. Just the casual thought of them reminds him of the aching, festering hole in his mind where their voices should be. But, something in him rails against giving up. He thinks that maybe it's the same something that told him to run for the first time all those years ago, the same something that said borrowing a TARDIS was a good idea (and it was right both times, so who is he to argue?). So, instead of thinking about everything that he has lost (destroyed), all the people he will never see again (children, grandchildren, friends, he closes his mind against the memories) he decides to visit Earth.
As soon as he steps out of the TARDIS, patting the worn wood in gratitude (because he still has a home, he could have nothing), he thinks maybe he should have gone to a deserted planet instead. There is a small group of children not fifteen feet in front of him; three boys he can tell just by looking at are big for their ages. They are kicking a dog, yelling abuse at the poor creature, and the Doctor almost revises his policy of 'no killing unless absolutely necessary'. But, he manages to hold his temper and watches as a woman comes running from her house, shaking her fist and snarling obscenities. Good, he thinks. The boys scatter and the dog gets up. It's not hurt and the woman seems to be taking good care of it so the Doctor moves on.
He spends the day wander the small village the TARDIS brought him to. He had been trying to get to London (he loves London), but somehow a sleepy town actually does him a lot more good than the bustling city ever would have. Silently, he thanks the TARDIS. As the sun starts to set he turns his feet towards home.
The TARDIS is parked in a neighborhood park, not looking out of place for once. The Doctor ambles though the green-space, enjoying the way the light filters through the branches (it's not orange, but it's pretty enough). He hears a voice. Someone is crying. Almost against his will he turns towards the noise. He never could resist children crying.
He sees the boy, curled up on the jungle gym before the child sees him. It's one of the tormentors from earlier. The Doctor almost leaves. Then he sees the kitten creeping toward the boy.
No! He wants to yell. Go Back! This one will do nothing but hurt you!
The words stick in his throat. He watches in paralyzed silence as the boy stops his sniffling and looks down at the tiny creature. He reaches towards it, fingers half curled, grasping. He picks it up. The Doctor's breath catches in his throat.
Please. He can't be sure if he whispered it or only thought it.
The boy's fingers tighten. The Doctor moves to save the poor thing.
Suddenly the boy's cries become sobs and he buries his face in soft fur. The kitten mews it's confusion.
The Doctor watches as the boy cries for a few minutes longer. Finally his sobs subside and he moves the kit from his face. He hold it up with gentle fingers. Wide green eyes meet watery brown.
"I didn't mean to," the boy confesses. The kitten starts purring, tiny tail swishing back and forth. "Ted and Harold said they wouldn't be friends with me anymore if I didn't."
The Doctor feels something inside himself heal just a little bit.
"I like dogs," the boy continues. The kitten mews, eliciting a wavering smile. "Cats, too." He sniffs. "I don't want to be their friend anymore. I don't want to have to- have to-" He can't put into words what he did and instead hugs the kitten close to his chest.
"I'm sorry," he whispers into the small ears. The Doctor smiles. This boy will never hurt another innocent, of that much he is absolutely sure. With a lighter heart, he completes his trip to the TARDIS. He doesn't feel quite so angry anymore.
There would be many times after that visit that he lost faith in Humanity, but he could always remember the feeling of hope he discovered watching a little boy vow to protect those less powerful than himself. He marked that memory as one of the best examples of human love. After that he learned to see it everywhere-
He saw their love in the simple wonder in their eyes when they looked at the night sky. That wonder kept him coming back because it reminded him of so very (very) long ago, when he was young and innocent and still had a home….
He saw it in the tight grips of young couples on the street, to whom everything seemed so vast and dangerous, conspiring to tear them apart, and in the gentle hold of the old, who understood that everything is fleeting and that holding on tighter doesn't necessarily help.
He saw it in the way random humans would go out of the way to help others. They would see someone in need, in pain, and drop everything to help them. Notes filled with love from strangers and people hugging random passersby just because they looked sad.
He saw it in the eyes of his companions who didn't care that he was a vile creature, a murderer of thousands. They only care that he was their Doctor, their friend, and they loved him more than words could say. They held his hand and hugged him, they kissed his cheek and rested their foreheads on his own. They showed him more wonders than he ever showed them. Sometimes he hated himself for taking so much from them and giving so little back.
The Doctor was amazed by the human capacity for love for it surpassed even their capacity for hate. It made their race seem perpetually young and innocent. He needed that. He would protect that. No matter what.