Antonyms of destructive :
constructive, formative, inferential, rehabilitative, reconstructive, creative, shaping, plastic, structural, advantageous, favorable, helpful, profitable, serviceable, beneficent, good, invigorating, rejuvenating, useful, beneficial, healthful, life-giving, salutary, wholesome, preservative, protective, productive, harmless, innocent, innocuous, inoffensive, ameliorative, healthy, nonfatal, nonlethal, salubrious, nondestructive, fluky, fortuitous, fortunate, happy, lucky, providential, auspicious, bright, encouraging, fair, golden, heartening, hopeful, optimistic, promising, propitious, rose-colored, rosy, upbeat.
Examples of usage:
The hardships of the camp and the campaign are more destructive of animal than human flesh. "Three Years in the Federal Cavalry", Willard Glazier.
Just two, just a man and a woman, emerging from all the destructive might of the world. "Dan Merrithew", Lawrence Perry.
That attempt is destructive to morals and dangerous to character. "The High Calling", Charles M. Sheldon.