If you are developing this using a language like Python or Java, you can use libraries like rarfile or unrar to automate the extraction attempt.
Before deleting the file, search for the exact filename of the RAR on Reddit enclosed in quotes. Example: "[Javakiba] MIAA-700.rar" . If someone solved it, they posted the solution five years ago. That solution is almost always in the top 3 of our Tier 1 list above. rar+password+list+for+javakiba