master key
square the circle
problem
trouble
entangled
enmesh
boil the ocean
hash out
rise to the occasion
rise to the challenge
hard yards
challenge
counseling
enodation
toughness
formidability
resource
ingenuity
lightning in a bottle
diagnostic
hard-set
crack
succour
megachallenge
hack
killer
ministration
succor
relief
rough sledding
pull teeth
hard time
task
superchallenge
mission impossible
snorter
rigour
pressure point
high-hanging fruit
bring off
navigate
over the river and through the woods
handful
spinous
waymaking
overchallenge
challengingly
finagle
hard going
marathon
torrid
endurance contest
hard nut to crack
solvability
solution
tough nut to crack
unwieldy
another string to one's bow
uncontrollable
heavy lifting
uphill
unmanageable
go at
counterdifficulty
voodoo
kink
mean
dys-
laborious
bitch
an old dog for a hard road
Rube Goldberg machine
skittish
pull through
pain point
convenient
tool
challengeful
escape fire
siege
dare
put a hurt on
conquest
torfer
puzzlery
defy
catch a cold
leg up
hard hit
imagination
feasibleness
resourcefulness
queer someone's pitch
kludge
three-pipe problem
do-or-die
doable
come to grips