Antagonism is a structure, not an affect. Within the antagonistic, so many emotions: agon, in Greek, meant gathering to watch a contest, but quickly took on the sense of the thing being watched, the struggle or contest. We struggle against and we struggle for, the latter being much more underdeveloped or abstract than the former.
Antagonism was developed by Ernesto Laclau and Chantal Mouffe, and taken up by Slavoj Zizek, to describe fundamental ruptures or contradictions or traumas in the social field, foundational clashes that structure experience and injustice amidst the apparent activity of destroying something in the environment of their activity. This negativity within the activity of the social might be class struggle, in whatever shape or might be a whole field of struggles and clashes that constitute the social field. That's a matter of debate.
What isn't a matter of debate is that contradiction/antagonism/foundational trauma is felt affectively in a different register from that in which it is experienced ideologically. Something is wrong in the social. One feels off, one feels the acid stomach of the broken circuit of social recognition, obligation, adequacy to life. The negative political affects judge the social in ways that the emotions express in displaced, distorted, but not untrue fashion.
See EMPIRE, a theory of massive, global inequality with the potential for massive, global, exuberant sublimation of antagonism. See [The Coming Community], which imagines the end of antagonism growing from the auto-poesis of people on the ground committed to being-with on the basis not of qualities, but of whatever. Arendt has a different view, seeing agon as the core energy of democracy.
sense of irreparable difference
affective state before coming into knowledge
anger circulates through the social but impersonal and not necessarily registered in the angry affects
producing antagonism as a political desire