The verb oppugn (oppugns, oppugning, oppugned) is used the same as its synonyms, "oppose," "question," "dispute," "challenge," or "disagree with." Example sentences:

His book was one of the first critical works to oppugn modernism.

I do not wish to oppugn the character by bearing false witness in regard to her activities.

He had the audacity to oppugn the director's decisions.

She was punished for being stupid enough to oppugn the conclusions of the head of the company.

He publicly oppugned the views in the book when he gave his speech.

Here's 44. You can pick the six you like:

align

antiforeign

arraign

assign

benign

campaign

champaign

codesign

coign

condign

consign

coreign

cosign

countercampaign

countersign

deign

deraign

design

eloign

ensign

feign

foreign

impregn

impugn

indign

malign

misalign

misassign

oppugn

outdesign

overdesign

preassign

realign

reassign

reconsign

redesign

reign

repugn

resign

sign

sovereign

thegn

unbenign

undersign

attune baboon balloon bassoon bestrewn boon buffoon cartoon cocoon commune coon croon doubloon dragoon dune festoon forenoon goon harpoon hewn immune impugn jejune june lagoon lampoon loon lune maroon mistune monsoon moon neptune noon oppugn platoon poltroon pontoon prune quadroon raccoon racoon rangoon roughhewn rune saloon shogun soon spittoon spoon strewn swoon teaspoon tribune triune tune tycoon typhoon walloon attune baboon balloon bassoon bestrewn boon buffoon cartoon cocoon commune coon croon doubloon dragoon dune festoon forenoon goon harpoon hewn immune impugn jejune june lagoon lampoon loon lune maroon mistune monsoon moon neptune noon oppugn platoon poltroon pontoon prune quadroon raccoon racoon rangoon roughhewn rune saloon shogun soon spittoon spoon strewn swoon teaspoon tribune triune tune tycoon typhoon walloon

align

antiforeign

arraign

assign

benign

campaign

champaign

codesign

coign

condign

consign

coreign

cosign

countercampaign

countersign

deign

deraign

design

eloign

ensign

feign

foreign

impregn

impugn

indign

malign

misalign

oppugn

outdesign

overdesign

preassign

realign

reassign

redesign

reign

repugn

resign

sign

sovereign

thegn

unbenign

Here are some possible words:

apache

apathy

apercu

apexes

aphids

apiary

apical

apices

apiece

aplomb

apneal

apneas

apneic

apnoea

apodal

apogee

Apollo

appall

appals

appeal

appear

appels

append

apples

appose

approx

aprons

aptest

epical

epigon

epilog

epizoa

epochs

eponym

ipecac

opaque

opened

opener

openly

operas

opiate

opined

opiner

opines

opiums

oppose

oppugn

optics

optima

opting

option

opuses

spaced

spacer

spaces

spaded

spader

spades

spadix

spalls

spanks

spared

sparer

spares

sparge

sparks

sparky

sparry

sparse

Sparta

spasms

spates

spathe

spavin

spawns

spayed

speaks

spears

specie

specks

speech

speeds

speedy

spells

spence

spends

sperms

spewed

spewer

sphere

sphinx

spicas

spiced

spicer

spices

spicey

spider

spiels

spiers

spiffy

spigot

spiked

spiker

spikes

spills

spilth

spinal

spined

spinel

spines

spinet

spinny

spiral

spirea

spired

spires

spirit

spirts

spital

spited

spites

splash

splats

splays

spleen

splent

splice

spline

splint

splits

splosh

spoils

spoilt

spoked

spoken

spokes

sponge

spongy

spoofs

spooks

spooky

spools

spoons

spoony

spoors

spored

spores

sports

sporty

spotty

spouse

spouts

sprain

sprang

sprats

sprawl

sprays

spread

sprees

sprier

sprigs

spring

sprint

sprite

sprits

sprout

spruce

sprucy

sprung

spryer

spryly

spuing

spumed

spumes

spunks

spunky

spurge

spurns

spurry

spurts

sputum

spying

upbeat

update

upends

upheld

uphill

uphold

upkeep

upland

uplift

uplink

upload

upmost

uppers

upping

uppish

uppity

uprear

uprise

uproar

uproot

uprose

upsets

upshot

upside

uptake

uptime

uptown

upturn

upward

upwind