: Many .rar archives from forums require a password, which is usually provided on the page where you found the link.
Given the name, this archive likely contains data related to the franchise, a famous series of fighting games developed by Rare and later Iron Galaxy. Depending on the file size, it could be: Killer.Instinct.part3.rar
: Use an up-to-date antivirus to check the files after downloading. : Many
: Only download archives from trusted communities to avoid "Trojan horse" files disguised as game data. Killer.Instinct.part3.rar