Opposite words for straighten:
bow, twine, entwine, kink, loop, turn, bend, coil, curve, flex, swirl, wind, spiral, curl, crook, round, hook, twist, arc.
Usage samples:
  1. " I guess things'll straighten out," he added.
    "Ethan Frome", Edith Wharton.
  2. Can't you straighten people out?
    "The Galaxy Primes", Edward Elmer Smith.
  3. She did not look at him, but had risen and begun to straighten out the papers beside her.
    "The Dwelling Place of Light, Complete", Winston Churchill Last Updated: March 5, 2009.
  4. He made an exclamation of surprise, and stole a quick glance at her, but she had bent down to straighten a shoe- buckle and he could not see her face.
    "The Long Lane's Turning", Hallie Erminie Rives.