Nina's conception of power can be understood can be understood, in Deleuze and Guattari's terms as a negative one. This concept of power is inspired by Spinoza and Nietzsche (Colebook in Parr, 2005: 215-217). From Spinoza they take the idea of power as potential and of joy the result of fulfilling this potential: “Joy, as the realisation of power, is therefore different from the moral opposition of good and evil, an opposition that impedes power by constraining it within some already given norm.” (215). In itself, this formulation might imply that Nina's murderous activities and desire for revenge are themselves neither good nor evil. Such a reading could accord with a more relativist reading of Nietzsche, insofar as the Christian virtue of forgiveness is read as a slave morality inversion of the preceding master morality of vengeance. This would also accord with the ethics of the Italian western and the vendetta, which Argento has spoken of favourably on occasion [quote from John Martin]. However, Deleuze here emphasises an equally Nietzschean distinction between active and reactive powers: “An active power maximises its potential, pushes itself to its limit and reaffirms the life of which it is but one expression. A reactive power, by contrast, turns back on itself.” (216) Cast in these terms, we may thus distinguish between the positive power of Leone, Bertolucci and Argento's avenger, Harmonica, and the one seeks vengeance upon, Frank, in Once Upon a Time in the West, and Nina and Roberto here.
Harmonica accepts that he is merely one expression of the old west, part of “an ancient race” whose role is now to helps bring into existence a new, feminine, west in which he knows and fully accepts that he has no place. Although Frank initially attempts to use his powers negatively to establish a place for himself in this coming world as a businessman like Morton, this reactive power turns back upon itself. For eventually he positively accepts of his equal obsolescence as one of the ancient race as he and Harmonica finally face off: “The future don't matter to us. Nothing matters now – not the land, not the money, not the woman. I came here to see you. 'Cause I know that now, you'll tell me what you're after.” Regardless of the which man wins this duel, the wider outcome, the birth of the new west, is assured. Their “large form” binominal leads to a new situation. The elegiac qualities of the film depend upon its ambiguity here, as to what this new situation represents: improvement, degeneration or an admixture of both. Cast in these terms, Harmonica and to a lesser extent Frank's becomings, like that of the west itself, are of a deterritorialising, becoming-woman type.
Nina's desire for vengeance upon her father is, by contrast, entirely reactive and negative. As we have seen, she is never positioned as looking towards the future, only the past, through the circling camera work. We get no sense of what her plans for life without her father and/or Roberto are, if any. As such, it makes sense that Nina should die rather than escape when her plans fail. Nina's becoming is of a territorialising, masculine, reactive type, one that can only turns back on itself in a destructive manner.