This section is from the book "Hill's Manual Of Social And Business Forms: A Guide To Correct Writing", by Thos. E. Hill. Also available from Amazon: Hill's Manual Of Social And Business Forms: The How-To-Do-Everything Book Of Victorian America.
Confederate - ally, accomplice, associate.
Confer - give, bestow, discourse, grant.
Confess - acknowledge, grant, own, admit, avow, recognize, disclose.
Confide - rely, trust, repose, depend.
Confident - impudent, bold, positive, dogmatical, absolute, assured.
Confined - limited, shut up, circumscribed, restrained, contracted, imprisoned.
Confirm - corroborate, establish, strengthen.
Conflict - contest, contention,fight, agony, combat, struggle, warfare, pang.
Conform - submit, yield, comply.
Confuse - stupefy, embarrass, confound, abash, disorder, perplex.
Congruity - agreement, consistency.
Conjecture - guess, think, belief, surmise.
Connected - joined, united, re-lated.
Connection - intercourse, union, commerce, association, communion.
Conquer - subdue, vanquish, overcome, surmount.
Conscious - aware, sensible, apprised.
Consent - yield, agree, assent, comply, acquiesce, accede.
Consequence - result, inference, effect.
Consequently - hence, accordingly, therefore, wherefore.
Consider - ponder, deliberate, regard, reflect.
Consign - entrust, commit, transfer, make over.
Consistent - agreeing, consonant, accordant, firm.
Console - comfort, soothe, cheer.
Conspicuous - prominent, noted, distinguished, illustrious.
Constancy - perseverance, firmness, steadiness, stability.
Constantly - ever, continually, perpetually, unchangeably, incessantly.
Construct - make, build, erect, form.
Consult - consider, deliberate, advise.
Consume - waste, destroy, absorb, complete.
Consummation - perfection, completion. Contagious - epidemic, infectious.
Contain - hold, include, embrace, comprehend.
Contaminate - pollute, taint, defile, corrupt, poison.
Contemn - scorn, despise, disdain.
Contemplate - consider, meditate, muse.
Contemptible - paltry, vile, disdainful, mean, despicable, disreputable, low.
Contend - quarrel, debate, contest, argue, vie, strive.
Contention - strife, conflict, contest, combat, dispute, dissension.
Contentment - acquiescence, happiness, satisfaction, gratification.
Contiguous - near, approximating, adjacent.
Continual - perpetual, constant, incessant, unceasing, continuous.
Continuation - continuance, duration.
Contract - arrangement, bargain, agreement, compact, covenant.
Contract - curtail, abridge, condense, abbreviate, reduce, shorten.
Contradict - gainsay, deny, oppose.
Contrary - opposite, adverse, inimical.
Contribute - assist, administer, aid, share.
Contrition - remorse, penitence, repentance, compunction, regret.
Contrivance - device, means, invention, plan, scheme.
Control - subdue, restrain, check, govern, curb.
Controversy - argument, debate, disputation, contest.
Convene - call together, assemble, convoke.
Convenient - handy, adapted, suitable.
Conversation - dialogue, discussion, conference, colloquy.
Converse - commune, speak, talk, discourse.
Convey - take, carry, bear, transport.
Conviction - persuasion, detection, satisfaction.
Convivial - agreeable, festal, social, sociable.
Convoke - gather, assemble, convene, call together.
Copious - ample, full, abundant, exuberant, plenteous, bountiful.
Cordial - hearty, warm, sincere.
Correct - mend, amend, reform, better, improve, rectify.
Corroborate - establish, confirm, strengthen.
Corruption - depravity, pollution, defilement, adulteration, contamination, infection, putridity.
Costly - expensive, precious, valuable.
Counsel - advice, instruction, exhortation.
Counteract - change, defeat, oppose, hinder, frustrate, prevent.
Countenance - uphold, favor, encourage, support, sanction.
Counterfeit - forged, feigned, false, spurious, imposture, imitation.
Couple - brace, pair, two, join, connect.
Courage - heroism, valor, bravery, firmness, intrepidity, fearlessness.
Course - mode, way, track, line, career, progress, method, passage, road, route, series, succession.
Courteous - kind, civil, affable, polished, respectful, polite, well-bred.
Covenant - arrangement, agreement, contract, pledge, stipulation.
Covering: - concealing, screening, sheltering, hiding, overspreading.
Covetousness - greed, avarice, cupidity, inordinate desire.
Coward - sneak, dastard, poltroon.
Cowardice - fear, timidity, cowardliness.
Crafty - underhanded, cunning, artful, wily, deceitful, sly, subtle.
Crave - beg, pray, beseech, entreat, implore, request, solicit, supplicate.
Create - build, form, make, cause, invent, originate, shape, produce.
Crime - evil, guilt, wickedness, sin, vice.
Crisis - juncture, critical point.
Criticism - stricture, censure, review, remark, judgment.
Crooked - bowed, turned, curved, awry, bent, disfigured, deformed.
Cross - ill-tempered, fretful, peevish, spleeny, petulant, splenetic.
Cruel - barbarous, brutal, pitiless, inhuman, inexorable, unmerciful, harsh.
Cultivation - advancement, civilization, improvement, refinement, tillage.
Cure - heal, restore, remedy. Curious - prying, inquisitive. Curse - imprecation, malediction, anathema, execration.
Cursory - hasty, careless, slight, desultory, superficial.
Curtall - shorten, contract, abbreviate, abridge.
Custom - habit, manner, usage, prescription, practice.
Damage - injury, hurt, loss, detriment.
Dampness - wet, moisture, humidity.
Danger - hazard, peril, risk, venture.
Daring - bold, fearless, valorous, courageous, intrepid, brave.
Dark - dismal, obscure, gloomy, dim.
Dead - still, lifeless, inanimate, deceased.
Deadly - fatal, mortal, destructive.