all-victorious
impregnable
indomitable
inexpugnable
insuperable
insurmountable
invincible
never-say-die
unbeatable
unsubduable
unsurmountable
unvanquishable
assiduous
constant
continuing
diligent
dogged
enduring
faithful
immutable
impassable
impenetrable
inalterable
incontestable
indefatigable
industrious
insistent
inviolable
invulnerable
irresistible
lasting
loyal
never-tiring
obstinate
overpowering
overwhelming
patient
patient as Job
permanent
perseverant
persevering
persistent
persisting
pertinacious
plodding
plugging
preoccupied
proof
rapt
relentless
resistant
resistless
resolute
secure
sedulous
deep-seated
ill-concealed
implacable
inborn
ineradicable
inextinguishable
instinctive
inveterate
unaccountable
uncontrollable
undying
unfailing
unflinching
unquenchable
unreasoning
unyielding