Tafsir of Al-Furqan 25:69

(Yudāʿafu lahu al-ʿadhāb) [The punishment will be doubled for him] on the Day of Resurrection. This is an appositive (badal) to yulqa [he will meet], either as an appositive of the whole for the whole (badal kull min kull) or an appositive of comprehension (badal ishtimāl). Apposition from a verb governed by a conditional is attested in the saying: "Whenever you come to us, you alight in our dwellings, you find plentiful firewood and blazing fire."

(Wa yakhludu fīhi) [And he will abide therein eternally]—that is, in the doubled punishment—(muhānā) [humiliated], meaning abased and despised. Thus, both bodily and spiritual punishment are combined for him.

Al-Ḥasan, Abū Jaʿfar, and Ibn Kathīr read yuḍʿafu with a yāʾ and in the passive voice, omitting the alif and the doubling. Shaybah, Ṭalḥah ibn Sulaymān, and also Abū Jaʿfar read nuḍʿifu with an initial nūn (vowelized with ḍammah), a kasrah on the ʿayn (doubled), and al-ʿadhāb in the accusative case. Ṭalḥah ibn Muṣarrif read yuḍāʿifu in the active voice, with al-ʿadhāb in the accusative. Ṭalḥah ibn Sulaymān read wa takhludu with a tāʾ of address, indicating a shift (iltifāt) that signals intense anger, in the nominative case. Abū Ḥaywah read wa tukhalladu in the passive voice, with a doubled lām and in the jussive mood; this is also narrated from Abū ʿAmr, as is the same reading but with a single lām. Abū Bakr, from ʿĀṣim, read yuḍāʿafu wa yakhludu in the nominative for both. Likewise, Ibn ʿĀmir and al-Mufaḍḍal, from ʿĀṣim, read yuḍāʿafu wa yukhalladu in the passive voice, nominative, with a single lām. Al-Aʿmash read with the yāʾ vowelized with ḍammah, in the passive voice, with a doubled lām and in the nominative case.

You have already learned the justification for the jussive. As for the nominative, its justification is that it is an inception (istiʾnāf), making the clause a state (ḥāl) for the subject of yulqa [he will meet]. The meaning is: "He will meet sin, with the punishment being doubled for him." The doubling of the punishment, in light of the Almighty's saying, "And the recompense for a sin is a sin the like thereof," and His, the Glorified's, saying, "And whoever brings a sin will not be recompensed except with its like," is said to be due to the addition of disobedience to disbelief. This is evidenced by the Almighty’s saying...