Monterey updates on imac won't install (12.1->12.2, 12.4->12.5)

The best antivirus, cleaning app, and overall maintenance app for Mac OS is Mac OS itself. All you need to do with Mac OS to keep it secure and running well is to keep it up-to-date and do periodic (about 1x per week) restarts. Other than that, leave it alone. Adding third party antivirus, cleaning, security and other types of maintenance apps to Mac OS adds no additional level of security. The only thing these apps do is have the opposite affect users want. They make Mac OS slow, unstable, generate odd behavior (much like you are experiencing) and make Mac OS appear buggy. 

Please locate the developers uninstall instructions for Proton VPN and follow to the letter. Then restart in Safe Mode per the directions in Use safe mode to isolate issues with your Mac and then restart normally. 

Also, unless you do not care about any of the data on your computer please begin to backup using Time Machine ( Back up your Mac with Time Machine ) you will need an External Hard Disk such as a OWC Mercury Elite Pro. Operating ANY computer without a sound backup plan is a 100% guarantee you will lose data that cannot be replaced.

It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community

Do you still run MS Windows on this machine? If you do not then uninstall Parallels, if you do continue to use Windows please, update Parallels.

However as previously stated, please uninstall the third party VPN app, at best it is worthless and is potentially damaging to Mac OS.

Unless your work provided the VPN app and it's paid for professional app, please uninstall!!!!

One thing that I noticed in the report is the high CPU usage of the pmset process. This process is related to power management. I also noted that you are using a Dell monitor.

• Top Processes Snapshot by CPU: (count) CPU (Source - Location) pmset 99.85%
• Top Processes Snapshot by Memory: pmset 1.38 GB

This shouldn't have anything to do with preventing your Mac from updating, but just wanted to point it out. FYI. I understand that the cause is Dell's Display Manager (DDM) that installed a LaunchDaemon that runs every 5 seconds. The daemon calls pmset to check if the Display is on. Removing the DDM app and all associated LaunchDaemons should resolve this issue.

Otherwise, I don't see anything outstanding in the report to identify the reason(s) you are unable to update your iMac.