Sunni theologians: a major sinner who has not committed unbelief remains a sinful believer. Many Khārijī groups: a major sin can make its perpetrator an unbeliever, though individual Khārijī formulations differed. The Muʿtazilah: classified the unrepentant major sinner in a station between the two stations, neither believer nor unbeliever, with a distinctive account of final punishment.
These are genuinely different doctrinal classifications. They should be represented separately rather than compressed into the uncontroversial statement that sin is morally wrong.
A reported formulation attributed to al-Hasan al-Basri calls the major sinner a hypocrite. The intended sense must be read with the distinction between hypocrisy of belief and hypocrisy of conduct.