He defies God by challenging the order of things, by being as great an amoralist as one presumes God to be a moralist.
From the time.com
An amoralist is not simply someone who is immoral, rather it is someone who knows what the moral things to do are, yet is not motivated to do them.
From the en.wikipedia.org
More examples
Someone who adheres to the doctrine that ordinary moral distinctions are invalid
Morality (from the Latin '' "manner, character, proper behavior") is a sense of behavioral conduct that differentiates intentions, decisions, and actions between those that are good (or right) and bad (or wrong). ...
(Amoralism) Moral nihilism (also known as ethical nihilism or amoralism), is the meta-ethical view that nothing is moral or immoral. For example, a moral nihilist would say that killing someone, for whatever reason, is neither inherently right nor inherently wrong.
One who practises or who advocates amoralism
(amoralism) Doctrine which advocates ignoring moral issues and norms