Synonyms of unfailing

1 Syllable

same, straight, loyal, sure, staunch, true

2 Syllables

yearlong, surer, come-through, foolproof, steadfast, faithful, trustier, there, solid, boundless, constant, endless, surest

3 Syllables

reliable, trustable, unflagging, ceaseless, persistent, perennial, continuing, perpetual, inerrant, eternal, unchanging, diligent, round-the-clock, consistent, bottomless, true-hearted, trustworthy, tried-and-true, aeonian, unwaning, weariless, continual, assiduous, fireball, unwearied, incorrupt, unerring, untiring, truehearted, continuous

4 Syllables

unretiring, surefire, dyed-in-the-wool, absolute, delivering, invariable, unrelenting, unlimited, unfaltering, high-principled, unaltered, unremitting, infallible, oft-repeated, inerrable, never-failing, apodictic, never-ceasing, dependable

5 Syllables

undeceivable, inexhaustible, unmodifiable, undiversified