Assalamu 'alaikum. Scholars say that shirk is the greatest oppression and he who commits shirk is the greatest oppressor. But Allah says in Quran ," And who are more unjust than those who prevent the name of Allah from being mentioned in His mosques and strive toward their destruction." (Surah Al Baqarah,114) . Allah also says in Quran," And who is more unjust than one who invents about Allah a lie or denies His verses?"(Surah Al An'am,21).Narrated Abu Huraira: I heard the Prophet (?) saying, "Allah said, 'Who are most unjust than those who try to create something like My creation?.........' "( Sahih al-Bukhari 7559).Apparently the opinion of the scholars, the verses of the Quran and the hadith seem contradictory so I am expecting a fatwa from you on this subject.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no doubt that Shirk (associating partners with Allah, The Exalted, in worship) is the worst form of injustice, as indicated by the Sharee‘ah texts. It is narrated on the authority of ‘Abdullah ibn Mas‘ood that he said: “I asked the Messenger of Allah, sallallaahu ‘alayhi wa sallam, which sin is the gravest in the Sight of Allah, and he said: ‘It is that you set a rival for Allah while He has created you.’ I said to him: ‘That is indeed grave.’” [Al-Bukhari and Muslim]

This does not contradict any of the texts you mentioned, because the 'greatest oppression' mentioned in these verses refers to oppression committed regarding the action mentioned in the verse respectively. For example, the one who prevents the name of Allah from being mentioned in His mosques is the greatest oppressor among those who prevent others from doing good deeds, and the one who invents lies about Allah is the greatest oppressor among those who invent lies. Allah, The Exalted, says (what means): {And who are more unjust than those who prevent the name of Allah from being mentioned in His mosques…} [Quran 2:114] This means that no prevention is more unjust than preventing the name of Allah from being mentioned in the mosques. Allah, The Exalted, also Says: {And who is more unjust than he who invents a lie about Allah?} [Quran 11:18] The meaning is that none of the inventors of lies is more unjust than the one who invents lies about Allah, The Exalted. And He also Says: {And who is more unjust than one who is reminded of the verses of his Lord but turns away from them…} [Quran 18:57] It means that none of those who turn away is more unjust than the one who, when reminded of the verses of his Lord, turns away from them, and so on.

Ash-Shinqeeti said in Daf' Eehaam Al-Idhtiraab ‘an Aayat Al-Kitaab, p.21:

Allah, The Exalted, Says (what means): {And who are more unjust than those who prevent the name of Allah from being mentioned in His mosques…} The interrogative form in the verse is intended for expressing disapproval and denotes negation. So the meaning is: there is none who is more unjust than the one who prevents the name of Allah from being mentioned in His mosques. However, there are other verses that denote a different meaning, like the verse (which means): {Then who is more unjust than one who invents a lie about Allah…} [Quran 6:144], {So who is more unjust than one who lies about Allah…} [Quran 39:32], {And who is more unjust than one who is reminded of the verses of his Lord but turns away from them…} [Quran 18:57] and other verses to this effect.

The following are some ways through which the above verses can be reconciled:

1- Linking each verse to the very subject it addresses, that is to say: none is more unjust, when it comes to the act of preventing, than the one who prevents others from mentioning the name of Allah in His mosques; and none is more unjust, in terms of fabricating lies, than he who fabricates lies about Allah, The Exalted. In this way, the verses are no longer conflicting.

2- They are described as the most unjust because it was they who had initiated the wrong act, meaning that none had preceded them in doing the wrong act, so they are judged to be more unjust than those who came after them and followed their wrong way. The meaning here, however, is connected to the idea highlighted in the previous point, because the initiation refers to the act of prevention and fabrication of lies, as far as the cited verses are concerned.

3- Another way, which was claimed to be the correct one by Abu Hayyaan, is to conclude that stating that ‘there is none who is more unjust’ does not necessarily mean that there is none who is equal in injustice. Hence, none of those examples of greatest injustice exceeds the others since they are all equal in the gravity of their injustice. Thus, the meaning is: there is none who is more unjust than the one who prevents the name of Allah to be mentioned in His mosques, and the one who fabricates lies about Allah, and the one who denies the verses of Allah. There is no problem with the fact that they are all equal in being the most unjust, and it does not entail that one of them is more unjust than the other. It is like saying, for example: ‘None is more versed in Fiqh than so-and-so and so-and-so.’ These two points were mentioned by the author of Al-Itqaan. [End of quote]

Allah Knows best.