فَأَمَّا مَن ثَقُلَتْ مَوَٰزِينُهُۥ ٦
Sentence structure
فَأَمَّا opens a detailed contrast. Conditional مَن is followed by ثَقُلَتْ as condition verb; مَوَٰزِينُهُۥ is its nominative subject with possessive هُ.
Ayah summary
Then the one whose scales of deeds are heavy will have a successful end.
فَأَمَّا — Then as for
Grammar: فَ resumes and أَمَّا is a particle of detailed division.
مَن — whoever
Grammar: A conditional noun introducing the detailed condition.
ثَقُلَتْ — are heavy
Grammar: A third-person feminine-singular perfect functioning as the condition verb.
مَوَٰزِينُهُۥ — his scales
Grammar: A masculine-plural nominative subject; attached هُ is possessive.