hard
obstinate
stubborn
unregenerate
adamant
adamantine
at a standstill
bowelless
bulky
bullheaded
cast-iron
certain
closed to
complaining
constant
cruel
dense
disputatious
disputing
dissentient
dissenting
dog-eat-dog
dour
durable
enduring
fated
fateful
firm
fixed
flinty
fractious
frozen
fundamentalist
grim
hard-core
hard-line
harsh
headstrong
heartless
heavy
hidebound
immobile
immotile
immotive
immovable
immutable
impenetrable
impersuadable
impersuasible
impervious
implacable
impliable
impregnable
defiant
indomitable
inexorable
inflexible
resolute
rigid
steadfast
stony
sturdy
tenacious
undaunted
unforgiving
unshaken
unswerving
Fielding
fielding
shielding
wielding
yielding