Reactionary (also reactionist) refers to any political or social movement or ideology that seeks a return to a previous state (the status quo ante). The term originated in the French Revolution, to denote the counter-revolutionaries who wanted to restore the real or imagined conditions of the monarchical Ancien Rgime.

Reactionists are on the far right of the political spectrum. Nazism is/was reactionary. Ipso facto, Nazism is on the far right of the political spectrum.

Hope that helps clear everything up.