(1) Kabt, i.e. debasement and humiliation of this world; and
(2) adhab muhin, i.e. a disgraceful torment that they will suffer in the Hereafter.
Tafsir Ibn-Kathir: (Explaining the Punishment of the Enemies of the Religion)
Allah states that those who defy Him and His Messenger and contradict His commandments, (كُبِتُواْ كَمَا كُبِتَ الَّذِينَ مِن قَبْلِهِمْ will be disgraced as those before them were disgraced) meaning, they will be humiliated, cursed and disgraced, just as what happened to their like were before them,
(وَقَدْ أَنزَلْنَآ ءَايَـتٍ بَيِّنَـتٍ And We have sent down clear Ayat.) meaning, none contradicts or opposes them, except a disbeliever, rebellious, sinner,
(وَلِلْكَـفِرِينَ عَذَابٌ مُّهِينٌ And for the disbelievers is a disgraceful torment) meaning, as just recompense for their arrogant refusal to follow, obey and submit to the religion of Allah.
Javed Ahmad Ghamidi Explanation:
This is a reference to the Hypocrites all of whose sympathies were with the enemies of Islam, in particular the Jews. They would launch a whispering campaign and a secret propaganda against any teaching of Islam they would regard as being against their desires. The purpose would be to create doubts in the minds of weak Muslims and strip them of their conviction in Islam.
Thus, their fate will be the same as the one met by the rejecters of the messengers of God after these messengers have conclusively communicated the truth to them. This is an established practice of God and He never changes this established practice. His law is the same for everyone.
Tafsir Qur'an Wiki:
The opening passage of the surah provided an aspect of the care shown to the Muslim community, while this second passage provides an aspect of antagonism to the opposite group who contend against God and His Messenger. The Arabic term, translated here as 'contend' is derived from the same root as the word used earlier, which means 'boundaries'. Thus, this group are defined as taking a stand at the other boundary, confronting God and His Messenger. This gives an image of two parties in contention and confrontation. As such, it serves to show their action in a very bad light. How miserable for a creature to be in open hostility to his Creator when it is He who provides him with sustenance.
These people who are in contention "shall be brought low as those who lived before them were brought low." The way this sentence is phrased in Arabic may be understood as a prayer against them. A prayer by God is a sentence of judgement that makes it inevitable since it is He who pronounces this sentence, and His will is always done. The phrase, those who lived before them,' refers either to earlier communities who were punished by God, or to the then unbelievers who suffered humiliating defeats at the hands of the Muslims prior to the revelation of this surah, as happened, for example, at the Battle of Badr.
"We have bestowed from on high clear revelations." This sentence separates the two fates suffered by the unbelievers in this life and in the life to come, in order to point out that both fates are clearly stated in these verses. It also tells us that these unbelievers do not face these fates as a result of ignorance or any ambiguity in the truth. Indeed, the truth has been put to them clearly and lucidly in these revelations, which they too have been given.
As the surah refers to their fate in the hereafter, it adds an inspiring comment that serves an educational purpose: "Shameful suffering awaits the unbelievers on the day when God will raise them all from the dead and tell them exactly all that they did in lift. God will have taken it all into account, even though they may have forgotten it. God is witness to all things. (Verses 5-6) They are made to suffer shame in punishment for their arrogance. This shameful suffering will take place on the day when all will be resurrected. Thus, it will be seen by all. Besides, the suffering is determined on the basis of a true account of their deeds. If they have forgotten these, God has recorded them all, as nothing escapes His knowledge: "God is witness to all things."
To sum the discussion on the aforesaid verse, let us say that God (with no assistance and associates) sent down His divine Wisdom in the shape of Commandments gradually, so that man could start to absorb them gradually. When communities enlarged, the requirements of imposition of Divine Law increased and Divine Books were revealed, each adding more to the previous. This finally culminated in the revelation of Qur'an, the last and the final Godly scripture for the guidance of mankind till the end of the earthly life. Hence, not accepting Qur'an but accepting the previous scriptures is sheer display of animosity to One True God and His final Messenger, Muhammad ﷺ.
Although, many a non-Muslims, especially adherents of the earlier Divine religions, have started to accept the Divine Wisdom contained in the Qur'an and Sunnah of Prophet Muhammad ﷺ, and entering the fold of Islam in large number, yet a majority is till hesitant to accept the truth, and show extreme hatred toward Islam and have unleashed campaign of Islamophobia to belittle Islam. They even taunt God of Muslims as something different from their God, in one case Gods, just to close their eyes from seeing and reading the truth contained in Qur'an.
But the world is getting wiser day by day as it is heartening to see more and more non-Muslims entering the fold of Islam through extensive reading of Qur'an, Sunnah and Hadith of Prophet Muhammad ﷺ and realizing that the hatred spread against Islam is only to escape from reality.