Proving this is a very high bar to meet for performance reviews.
Most formal performance reviews will be on a carefully worded standard form where literally nothing the manager selects can be libel, and even for informal references, most criticism (even if unwarranted!) is not libel.
If a form asks "How satisfied are you with 29athrowaway's performance this year? " then answering "1/10" is opinion, not fact, and also likely to be true opinion. A written statement "29athrowaway has absolutely not met my expectations this year" is very difficult to be proven false, it's plausible that these expectations indeed were not met. "29athrowaway has never ever done anything right since they were born" is rhetorical hyperbole and generally not treated as libel despite being technically not true. "I think 29athrowaway should be fired" is not purporting to be fact. "29athrowaway was rude to customers three times in the last week" is extremely hard to prove as false even if it is pulled out of thin air; even if you have all the interactions recorded, there's probably something which can interpreted that way. "29athrowaway did not fulfill their tasks in project XYZ" is a tricky one (and so most formal performance review forms will never include statements worded like that, at least if they're approved by HR/legal), but depends mostly on how well documented the assignments were, and if they can somehow be stretched to assert that you performed only 99% of them, that's not really libel.
Power corrupts and absolute power corrupts absolutely.
When you are given authority, some will use it fairly, others will not.
Some will use authority to advance their own careers at the expense of the careers of others, and create a system where loyalty, not merit, is used to rank employees.
People with psychopatic and narcissistic traits are entitled to become managers. We need psychological testing to weed them out of companies.
Psychopaths create a psychopatic fiction based on manipulation and lies. We need to make it costly so it stops.
Most formal performance reviews will be on a carefully worded standard form where literally nothing the manager selects can be libel, and even for informal references, most criticism (even if unwarranted!) is not libel.
If a form asks "How satisfied are you with 29athrowaway's performance this year? " then answering "1/10" is opinion, not fact, and also likely to be true opinion. A written statement "29athrowaway has absolutely not met my expectations this year" is very difficult to be proven false, it's plausible that these expectations indeed were not met. "29athrowaway has never ever done anything right since they were born" is rhetorical hyperbole and generally not treated as libel despite being technically not true. "I think 29athrowaway should be fired" is not purporting to be fact. "29athrowaway was rude to customers three times in the last week" is extremely hard to prove as false even if it is pulled out of thin air; even if you have all the interactions recorded, there's probably something which can interpreted that way. "29athrowaway did not fulfill their tasks in project XYZ" is a tricky one (and so most formal performance review forms will never include statements worded like that, at least if they're approved by HR/legal), but depends mostly on how well documented the assignments were, and if they can somehow be stretched to assert that you performed only 99% of them, that's not really libel.