Is it considered an injustice or a sin for me to evaluate employees' performance using specific percentages imposed by the company, which may lead to some of them receiving an undeserved low evaluation, given that these percentages are a condition for submitting the evaluation?

The employee evaluator must be truthful and just, because his evaluation is a testimony for which he will be questioned on the Day of Resurrection. False testimony is one of the gravest sins, and he bears responsibility for any deprivation or harm to the employee that results from his evaluation. Allah Almighty says: (Indeed, Allah commands you to render trusts to whom they are due and when you judge between people to judge with justice) and Allah Almighty says: (And when you speak, then be just, even if it is [regarding] a near relative). If employees are equal, it is not permissible to differentiate them in grades, and the company must be informed of this or an apology for the evaluation must be offered. If there is a slight difference between them, it must be recorded in a way that does not wrong anyone.