trickiness
challengingness
ruggedness
hardness
trouble
problem
challenge
rigour
hydra
hard-set
tricksiness
toughness
difficultate
difficultness
stumpiness
doo-doo
mean
formidability
elusiveness
enmesh
trickishness
praemunire
complicatedness
resource
trickily
rough sledding
hard time
dauntingness
daunting
hard yards
beleaguered
over the river and through the woods
mountain
hard nut to crack
toughening
adeptness
strainedness
mountain to climb
difficulty level
carefulness
tough nut to crack
pain point
arduity
appeal
hurdlesome
torfer
bad
try as one may
ambitious
run for one's money
curly
spinous
tediousness
Matterhorn
difficult
induration
mode
bring off
push shit uphill
skiddly
perplexed
challengeable
pull teeth
effortfulness
testingly
asperity
eke out
rub
fractious
uneasy
undemandingness
difficulty
impeded
adequateness
querulousness
multichallenge
tall
copout
catch a cold
adequacy
conquest
schemingness
superchallenge
trenchantness
torrid
problematicality
an old dog for a hard road
come at
rough
handiness
problematicness
pull off
snag
endeavor
hardpressed