The Collaborative International Dictionary of English v.0.48:

Suasive \Sua"sive\, a.
   Having power to persuade; persuasive; suasory. --South.
   "Genial and suasive satire." --Earle. -- Sua"sive*ly, adv.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "suasive":
   authoritative, cajoling, charismatic, charming, consequential,
   effective, effectual, efficacious, enchanting, estimable,
   exhortative, exhortatory, hortative, hortatory, important,
   influential, magnetic, momentous, personable, persuading,
   persuasive, potent, powerful, prestigious, reputable, strong,
   substantial, telling, weighty, wheedling, winning