incontestable
incontestible
resolute
abiding
balanced
cool
fast
fiducial
firm
firm as Gibraltar
fixed
imperturbable
in equilibrium
predictable
reliable
secure
solid
sound
stable
steadfast
steady
substantial
unflappable
unflinching
unwavering
well-balanced
without nerves
dauntless
firmest
hard-won
immovable
indomitable
newfound
overweening
stoic
unalterable
unassailable
undying
unfailing
unflagging
unhesitating
unshakeable
unshaken
unshrinking
unswerving
unyielding
well-founded
breakable
unbreakable
unmistakable
shakable