Grave punishment also knows as Adhaab of Qabr, it means to get punished in Grave for the prohibited things you did during your lifetime.
Furthermore, Holy Prophet (PBUH) was also shown the people who committed adultery (Zina).
Holy Prophet (PBUH) also witnessed the people who used to lie a lot.
3. Missing a Prayer
On the night of Isra and Meraj, Two angels showed Holy Prophet (PBUH) people who are being punished by smashing a rock in their head for missing three obligatory daily prayers.
We must see backbiting as the most discuss thing in our society whether its Men or Women they tend to Gossip and backbite whenever they meet. And this is what Hadith has said about backbiting and its punishment.
As per several Quranic verses and Hadiths, Hypocrites will be on the lower most level of Hell. Allah has also warned us in Quran.
Shirk is one of the things which Allah will never forgive. We have also compiled the types of Shirk one does in a blog post. This is what Allah says in Surah Inaam Verse 93 about Punishment in grave for Shirk.
May Allah keep us all away from such sins.