Shirk

 First, the Greatest Sin - Shirk

The greatest sin in the sight of allah the Exalted is to associate a partner with Him while He alone created you. Allah will never forgive the sin of shirk as He explained,

Verily, Allah forgives not that partners should be set up with him in worship, but He forgives except that (anything else) to whom He pleases, and whoever sets up partners with Allah in worship, he has indeed invented a tremendous sin. (Surah An-Nisaa: 48)

On that day, false deities will disown their wotshippers and they will acknowledge Allahs supermacy. Allah will upbraid the mushrikeen as He says,

And it will be said to them: Where are those (the false gods whom you used to set up as rivals with allah) that you used to worship instead of Allah? Can they help you or (even) help themselves. (Surah Ash-shu´araa: 92-93)

He also says,

And (remeber) the Day when He (your Lord Allah) will call them (those who worshipped others along with Allah), and will say: Where are My (so-called) partners, whom you used to assert. (Surah Al-Qasas: 74)

Those who used to slaughter for other than Allah will be questioned; such as those who use to make offerings to idols or graves, as Allah says,

And they assign a portion of that which We have provided them unto what they know not (false deities). By Allah, you shall certainly ne questioned about (all) that you used to fabricate. (Surah An-Nahl:56)

They will be asked about their denial of the Messenger as Allah mentions,

And (remeber) they Day (Allah) will call to them, and say; What answer gave you the Messengers? Then the news of a good answer will be obscured to them on that day, and they will not be able to ask one another. (Al-Qasas: 56-66)

Second, the servant will be questioned about what he did in his lifetime: The servant will be asked about his actions - good or bad. This is as Allah says,

So, by your Lord (O Muhammad salla alayhi wa sallam), We shall certainly call all of them to account. For all that they used to do. (Surah Al-Hijr: 92-93)

Yes, all of them would be asked in their entirety - the rich and the poor, the king and the leader, the Arabs and the non-Arabs, the white and the black, the freeborn and slave - all of them would be questioned about what they used to do.

Even the Messengers will be asked concerning their communities. The communities will also be asked concerning the Messengers sent to them. This is as Allah says,

Then surely, We shall question those (people) to whom it (The Book) was sent and verily, We shall question the Messengers. Then surely, We shall narrate unto them (their whole story) with knowledge, and indeed We were not absent. And the weighing on that day (Day of Resurrection) will be the true (weighing). So as for those whose scale (of good deeds) will be heavy, they will be the successful (by entering Paradise). And as for those whose scale will be light, they are those who will lose their own selves (by entering Hell) because they denied and rejected Our Ayat (Proof, evidences, verses, lessons, signs, revelations, etc). (Surah Al-A´raaf:6-9)

The Messenger of Allah salla alayhi wa sallam said,

The feet of a slave will not shift on the Day of Resurrection until he is asked about for things: about his lifetime, in what (endeavour) did he spend it, about his knowledge, how did he act with it, about his wealth, how did he earn it and on what did he spend it and about his body, on what did he wear it out.