The people who will receive the hardest punishment...

بسم الله والحمد لله والصلاة والسلام على رسول الله ، وبعد

Ibn `Umar said: “Three groups of people will receive the severest type of punishment on the Day of Judgment: the hypocrites, from the companions of al-Maa’idah who did kufr, and Fir`aoun and his associates.”

The evidence for this is in the Book of Allaah تبارك وتعالى:

{إن المنافقين في الدرك الأسفل من النار} [النساء: 147]

{Verily, the hypocrites will be in the lowest depth (grade) of the Fire} [Surah al-Nisaa' (4):147]

And Allaah تعالى said about the companions of al-Maa’idah (the table spread with food):

{فإني أعذبه عذابا لا أعذبه أحدا من العالمين} [المائدة : 115]

{Allaah said: “I am going to send it down to you, but if any of you after that disbelieves, then I will punish him with a torment such as I have not inflicted on anyone among (all) the `aalameen (mankind and jinn)”} [Surah al-Maa’idah (5): 115]

And He تعالى said about the Fir`aun and his people:

{أدخلوا آل فرعون أشد العذاب} [غـافر : 46]

{And on the Day when the Hour will be established (it will be said to the angels): “Cause Fir`aun’s (Pharaoh's) people to enter the severest torment!”} [Surah Ghaafir (40): 46]

[Tafseer al-Qurtobee]