Synonyms of undefeatable

1 Syllable
staunch
2 Syllables
willful, stubborn, ruthless, dogged
3 Syllables
unflinching, bulletproof
4 Syllables
impregnable, resolute, obstinate, pertinacious, invincible, impassable, unbeatable
5 Syllables
indomitable, invulnerable, insurmountable, unassailable, insuperable, unattackable, unconquerable, unsurmountable