And thus We have placed within every city the greatest of its (6:123)

﴿وَكَذَٰلِكَ جَعَلْنَا فِي كُلِّ قَرْيَةٍ أَكَابِرَ مُجْرِمِيهَا لِيَمْكُرُوا فِيهَا ۖ وَمَا يَمْكُرُونَ إِلَّا بِأَنفُسِهِمْ وَمَا يَشْعُرُونَ﴾
[ الأنعام: 123]

6:123 And thus We have placed within every city the greatest of its criminals to conspire therein. But they conspire not except against themselves, and they perceive [it] not.

Just as what transpired with those leaders of Mecca who committed polytheism and barred others from the Way of Allah, He has placed leaders and influential people in every town who use various means and schemes to call towards the path of Satan and oppose the messengers and their followers.
In reality, their scheming and planning will eventually only harm them, but they do realise this due to their ignorance and their following of desires.

And thus We have set up in every town great ones of its wicked people to plot therein. But they plot not except against their ownselves, and they perceive (it) not.

phonetic Transliteration

Wakathalika jaAAalna fee kulli qaryatin akabira mujrimeeha liyamkuroo feeha wama yamkuroona illa bianfusihim wama yashAAuroona

Abdullah Yusuf Ali - Translation

Thus have We placed leaders in every town, its wicked men, to plot (and burrow) therein: but they only plot against their own souls, and they perceive it not.

Safi-ur-Rahman al-Mubarakpuri

And thus We have set up in every town great ones of its wicked people to plot therein. But they plot not except against themselves, and they perceive (it) not.

Page 143 English transliteration