What is better in the eyes of the Qur'an and the Sunnah? Wearing the Hijab, but cheating her husband and being a bad person? Or a person that never harmed anyone and believes in Allah and his Prophets but doesn't wears the Hijab?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. Hijab is an obligation upon any Muslim female who has reached the age of puberty. Similarly, the obedience of one's husband, the preservation of his honour and wealth are obligations upon the wife. So, any woman who wears Hijab and deals diligently with her husband fulfills both the right of the husband and that of Allah. Such a woman is without doubt the most highly ranked. But if the woman wears Hijab but abuses of her husband's rights, she mixes a good deed and a bad one which means that she gets reward for the first deed and will be punished for the second one. She should do what Allah orders her to do and leave anything that is forbidden by Allah. the same thing should be told to the second woman who claims believing in Allah and His Prophet (Sallallahu Alaihi wa Sallam) and being good but refuses to wear Hijab. This woman should know that her true belief in Allah and His Prophet (Sallallahu Alaihi wa Sallam) is materialized in her abiding by their orders and avoiding things they prohibited. No doubt that Hijab is among the things that Allah has imposed upon Muslim women. Allah Says (interpretation of meaning): {…that they should draw their veils over their bosoms and not display their beauty except to their husbands,…}[24:31]. So, to this woman, we say, "You should put on Hijab immediately and follow the Orders of Allah". As for your question "Who is better between the two women?" this is known only to Allah. It depends on the fear and awe they have. The degree of fear and awe in their hearts is known to Allah only and it is Him who knows which one of them fears Him more. Allah knows best.