Synonyms for Severe:

adj.

accurate (adjective)
proper, punctilious, scrupulous, discriminating, correct, particular, methodical, literal, careful, meticulous.
acute (adjective)
stabbing, powerful, desperate, piercing, keen, excruciating.
all (adjective)
terrible, wicked.
ambitious (adjective)
formidable, difficult, strenuous.
arduous (adjective)
laborious, troublesome, trying, painful, burdensome, grueling, onerous, uphill, rough.
ascetic (adjective)
miserly, lenten, stark, teetotaling, dry, monastic, stoic, austere, trappist, spartan, penitential, parsimonious, celibate, repentant, abstinent, franciscan, abstemious, ascetic, hermit-like.
austere (adjective)
stark, plain, spartan, spare.
authoritarian (adjective)
autocratic, unyielding.
bald (adjective)
blunt.
brutal (adjective)
gruff.
difficult (adjective)
knotty, arduous, rugged, cantankerous, laborious, onerous, tricky, rough, demanding, formidable, complex, troublesome, stressful, bothersome, fussy, contrary, strenuous, harsh, adverse, thorny, grinding, toilsome, finicky, uphill, burdensome, tough, wearying, oppressive, difficult, complicated, wearing, tight, cumbersome, trying, ticklish, hard, wearisome.
effortful (adjective)
effortful.
extreme (adjective)
radical, intense, drastic, extreme, excessive.
fastidious (adjective)
fastidious, squeamish, hypercritical, careful, finicky, flawless, priggish, fussy, critical, discerning, choosy, prudish, methodical, Qualmish, exacting, dainty, literal, meticulous, accurate, mincing, discriminating, perspicacious, demanding, prim, correct, picky, scrupulous, precise, diligent, conscientious, proper, persnickety, delicate, rigorous, particular, epicurean, punctilious.
painful (adjective)
irritating, bothersome, horrendous, unbearable, excruciating, oppressive, withering, disagreeable, painful, harrowing, Torturing., trying, grievous, biting, odious, Besetting, crushing, sore, Gnawing, stinging, insufferable, miserable, arduous, distressful, aching, cruel, piercing, wrenching, tormenting, agonizing, throbbing, hurtful, woeful, aggravating, inflaming, stabbing, Irksome, smarting, acute, cutting, offensive, Cramping, bitter, troublesome, burdensome, unpleasant, grueling, uncomfortable, chafing, annoying, anguishing.
precise (adjective)
accurate.
severe (adjective)
despotic, relentless, pitiless, keen, cool, effortful, icy, close, peremptory, sore, brisk, demanding, curt, bleak, strait-laced, stiff-necked, implacable, earnest, intolerant, disciplined, tart, abrupt, meticulous, inconsiderate, draconian, cold, intense, arduous, cutting, obstinate, basic, distressing, acute, piquant, short, sharp, frosty, strict, tyrannical, acrimonious, lean, astringent, stark, critical, raw, grim, grinding, austere, hefty, chilly, forbidding, overbearing, uncompromising, mordant, ascetic, resolute, rugged, inflexible, cruel, prudish, precise, domineering, serious, dangerous, firm, blunt, gruff, biting, unchanging, brusque, unalterable, bitter, grave, strenuous, tough, wicked, exacting, caustic, dry, unpleasant, dour, drastic, authoritarian, censorious, correct, fundamental, inclement, extreme, unfeeling, spare, stern, taxing, harsh, rigorous, hard, obdurate, rigid, toilsome, puritanical, imperial, hidebound, stringent, unbending, spartan, oppressive, crisp, acerbic.
sharp (adjective)
sharp.
sober (adjective)
disciplined.
wicked (adjective)
wicked.

n.

desperate, profound. disturbing, unyielding, alarming, distressing, worrying, anxious, tense. hot, attitude, be an effort. comfort, brutal, hardline. hefty, unappealing, unattractive, powerful, big, grotesque, hideous, unsightly, ugly. important, sultry, threatening, momentous, earnest, humid, inclement, unseasonable, muggy. help. exigent, effortful, taxing. severe (noun)
grievous, critical, austere, knockout, terrible, nonindulgent, intense, strong, wicked, strict, dangerous, bad, stark, serious, grave, plain, hard, spartan.
unfriendly (noun)
churlish, antagonistic, unfriendly, stony, cold, aloof, distant, hostile.

Other synonyms:

effortful, hardline, cold, humid, worrying, distressing, sultry, muggy, forbidding, desperate, unseasonable. powerful, tense, brutal, pitiless, threatening, momentous, profound. anxious. unyielding, earnest, taxing, hefty. demanding
exigent.
disquieting
disturbing.
harsh
peremptory.
ruthless
inclement.
stringent
mordant.
Other relevant words:
plain, serious, cold, inclement, grave.

Usage examples for severe

  1. " Miss Puttenham says she is quite beautiful still, in a wonderful, severe way. – The Case of Richard Meynell by Mrs. Humphrey Ward
  2. The fighting here was not severe – Comic History of the United States by Bill Nye