ثُمَّ لَنَنزِعَنَّ مِن كُلِّ شِيعَةٍ
...
Then indeed We shall drag out from every sect,
This means from every nation.
This is what Mujahid said.
...
أَيُّهُمْ أَشَدُّ عَلَى الرَّحْمَنِ عِتِيًّا
all those who were worst in obstinate rebellion against the Most Gracious.
Ath-Thawri reported from Ali bin Al-Aqmar, from Abu Al-Ahwas, from Ibn Mas`ud that he said,
"The first of them will be bound to the last of them until their number is complete. Then, they will be brought all together. Then, Allah will begin with the greatest of them in crime and continue in succession.
That is Allah's statement,
ثُمَّ لَنَنزِعَنَّ مِن كُلِّ شِيعَةٍ أَيُّهُمْ أَشَدُّ عَلَى الرَّحْمَنِ عِتِيًّا
Then indeed We shall drag out from every sect all those who were worst in obstinate rebellion against the Most Gracious.
This is similar to Allah's statement,
حَتَّى إِذَا ادَّارَكُواْ فِيهَا جَمِيعًا قَالَتْ أُخْرَاهُمْ لاٍّولَـهُمْ رَبَّنَا هَـوُلاءِ أَضَلُّونَا فَـَاتِهِمْ عَذَابًا ضِعْفًا مِّنَ النَّارِ
Until they will be gathered all together in the Fire. The last of them will say to the first of them: "Our Lord! These misled us, so give them a double torment of the Fire." Until His saying,
بِمَا كُنتُمْ تَكْسِبُونَ
(For what you used to earn). (7:38-39)
The first of them will say to the last of them: "Your were not better than us, so taste the torment for what you used to earn."
Concerning Allah's statement,
ثُمَّ لَنَحْنُ أَعْلَمُ بِالَّذِينَ هُمْ أَوْلَى بِهَا صِلِيًّا