Synonyms for Arrant (same or very similar meaning)
WordNet sense 1 (without qualification; used informally as (often pejorative) intensifiers):
complete, consummate, everlasting, gross, perfect, pure, stark, thoroughgoing, unadulterated, utter, double-dyed, sodding, staring, consummate, perfectWordNet sense 2 (not diminished or moderated in intensity or severity; sometimes used as an intensifier):
unmitigatedFrom the ODE community, based on WordNetadd/edit