Is there a contradiction between verses 68 and 69 of Surah Al-Furqan, which associate idolatry and unlawful sexual intercourse with punishment, and verse 48 of Surah An-Nisa, which states that idolatry alone is unforgivable, and that sins other than that are subject to Allah's will?

The noble verses clarify that whoever dies in a state of polytheism, Allah will not forgive him. As for whoever repents before death—whether he was a polytheist or committed major sins—Allah accepts his repentance and forgives his sin. So, whoever dies a polytheist is in the Fire. And whoever repents before his death, Allah forgives him, even if he was a polytheist. And whoever dies having committed major sins but without associating partners with Allah, he is under Allah's will. Even if he is punished, he will not remain eternally in the Fire, and his ultimate destination is Paradise.