Oroku Saki doesn't regret. Even more importantly, he can't regret for what he's done was right and just and needed to be done.
The Hamato Clan was destroyed, and it was all thanks to him.
He's the heir of the Foot Clan so it was his duty to let them pay for the death of his people.
It doesn't matter that the Hamatos let him live and raised him alongside their own heir, Hamato Yoshi.
And it doesn't matter that Hamato Yoshi has been like a brother to him. No, not like a brother, he's been his brother.
And now he's dead.
Saki himself saw him being buried under these burning beams.
No one can survive that, not even a ninja as skilled and strong as Yoshi.
For a moment, Saki feels something, but he reminds himself that he isn't allowed to feel anything else than satisfaction. The deed is done. His clan has been avenged, and the Hamatos are destroyed, once and for all.
They should have seen it coming, but the Hamatos, they've always been too kind. Otherwise they would have killed him all these years ago with the rest of his clan. And they should have, for in this world, there is no place for kindness.
They shouldn't have lied to him all these years, only to tell him the truth one day. Lies should always be lies, that's why they are lies.
But they did tell him the truth because it was the right thing to do.
These Hamatos, so kind and noble. And now so dead.
He's done the right thing tonight. Avenging your people, that's the right thing, isn't it?
A picture of Tang Shen flashes before his mind's eye, and for the first time, he allows the feeling to spread.
The pain of losing her.
She shouldn't have gotten in the way, it was her own fault. It all happened too fast, he hasn't been able to stop, not even if he wanted, and oh, he wanted to!
No, she shouldn't have gotten in the way, giving her life for the man who's been his brother for so long and turned into his enemy by blood in the course of a story. A story they call truth.
But Saki has some truth for them now as well: He's done the right thing.
It was his duty as the last of the Foot Clan, and he did good.
The Hamatos are gone, only the Foot Clan is left.
It was right, it was just, and it is done.
No, Oroku Saki doesn't regret. All he feels is satisfaction and power.
And whatever it is that is curling in his guts, that is making him feel all cold and sick, it has to be something else.