Is it permissible to supplicate against specific individuals, following the example of the Messenger of Allah (peace be upon him) in the incident of Bi'r Ma'unah when he supplicated against Amir ibn al-Tufayl or his tribe?

It is permissible to supplicate against an oppressor, whether by specifically naming them or in general terms. It is authentically reported that the Prophet, peace and blessings be upon him, supplicated against the tribes of Ra'l, Dhakwan, Banu Lihyan, and Usayya for thirty mornings, and likewise his supplication against Mudar. Also, the Qur'an records the supplication of Musa (Moses), peace be upon him: "Our Lord, obliterate their wealth and harden their hearts so that they do not believe until they see the painful punishment" (Yunus: 88).