What is the wisdom behind the word (مِّنْ) [min] in the verse: (And We will surely make them taste of a severe punishment) [Quran 32:21], and is it for partiality?

The preposition "min" (مِن) is used to denote a part of a whole (tab'id), to specify the genus or kind (bayan al-jins), and to indicate the starting point in places and times. It can also be an extra particle (za'idah) for emphasis. In the verse, ﴿وَلَنُذِيقَنَّهُمْ مِّنْ عَذَابٍ غَلِيظٍ﴾ (And We will surely make them taste a severe punishment), the most probable meaning of "min" here is for specifying the genus (bayan al-jins), or it is for denoting a part of a whole (tab'idiyyah). Both meanings convey immense severity and gravity.