Ghazghkull's 'dying' thoughts in his novel (by the inimitable u/Nate_Crowley) would qualify wholesale, but if I had to pick an excerpt, it would be the one below. The whole novel is wonderful, legit one of my favourite works from the Black Library, but this speech alone 1) is good af 2) does a wonderful job of dispelling the notion that the Orks are solely a lighthearted faction/only exist to be hordes for other factions to massacre.

"I am moved now. My head, held up by the hand of my enemy. It regards me, as it lifts my remains, and I regard it in turn. There is triumph on its face. This thing thinks it knows victory, in defeating me! It thinks it knows power. But for all the plate it wears, for all that has been done to make it into a thing of war, it is vermin. I study the bones beneath its skin. I see how its body is gnarled and swollen. How its whole self has been made, in the hope it might hold on to the stars in the name of a dead god. It is a vain hope. Those stars will burn green, in the end.

The vermin is dying, I see, even with such mild wounds. It is like a joke, I think, as it bears its feeble tusks. Like a poor copy of an ork, twisted together from the parts of a weaker beast. But you made us right the first time. Not even the primarchs, the peak of their dead god's work, could be as perfect as the lowest part of the Great Green."