Synonyms of effectual

1 Syllable
strong, sound
2 Syllables
lawful, soundest, telling, binding, helpful, valid, trenchant, legal, potent, sounder, licit, phenom, virtuous
3 Syllables
successful, achieving, capable, effecting, qualified, inerrant, sovereigns, efficient, forcible, fulfilling, workable, clean-living, sovereign, powerful, impactful, monarchal, proficient, undecayed, useful
4 Syllables
adequate, inerrable, nimble-witted, high-powered, accomplishing, self-governed, decisive, productive, efficacious, infallible, profitable, conclusive, apodictic, convictive, self-sustaining, effective, well-constructed, serviceable, expeditious, practicable, persuasive
5 Syllables
undeceivable
6 Syllables
determinative