obstinate
stubborn
unregenerate
adamant
assiduous
badgered
baited
balking
balky
bedeviled
beset
bigoted
bugged
bulldogged
bulletheaded
bullheaded
bullyragged
case-hardened
chivied
committed
constant
continuing
determined
deviled
diligent
dogmatic
enduring
faithful
fanatic
fretted
harassed
hardheaded
harried
haunted
headstrong
heckled
hectored
hounded
immutable
inalterable
indefatigable
indomitable
industrious
inexorable
insistent
intolerant
invincible
lasting
loyal
morose
mulish
needled
never-tiring
bogged
clogged
logged