“Is one who is a believer like one who is defiantly disobedient?” (Qur'an 32:18).
Some used this contrast to argue that every fāsiq is outside faith. The response examines the verse's context: fāsiq may here refer to a person whose rebellion includes unbelief. Such use does not establish that every major sinner is the subject of this contrast.
An expression that denotes one category in a particular context does not necessarily have the same restricted meaning wherever it appears. Contextual interpretation is essential.