complete, total, utter
blatant, flagrant
callous, cavalier, cynical
reckless, wanton
their reckless disregard for human life

blithe, fine (ironic, esp. BrE)
With a fine disregard for geography, she decided to drive to the island.

apparent

demonstrate, show

disregard for
He showed complete disregard for the feelings of his family.

disregard of
their flagrant disregard of the rules

Disregard is used with these nouns as the object:
advice, comment, rule, wish