WordNet sense 1 (severely simple):

severe, stern, austere

WordNet sense 2 (not elaborate or elaborated; simple):

plain

WordNet sense 3 (not within reasonable limits):

immoderate

WordNet sense 4 (without qualification; used informally as (often pejorative) intensifiers):

arrant, complete, consummate, everlasting, gross, perfect, pure, thoroughgoing, unadulterated, utter, double-dyed, sodding, staring, consummate, perfect

WordNet sense 5 (not diminished or moderated in intensity or severity; sometimes used as an intensifier):

unmitigated

WordNet sense 6 (providing no shelter or sustenance):

bare, barren, bleak, desolate, desolate

WordNet sense 7 (unfavorable to life or growth):

inhospitable

WordNet sense 8 (devoid of any qualifications or disguise or adornment):

blunt, crude

WordNet sense 9 (not conditional):

unconditional