Kenel panic after updated to Big Sur 11.1 when shutdown my iMac

You likely have a hardware problem, but it could have been something that BrickMyMac "cleaned" that was a required part of the OS.

You should take it to an Apple Store or Authorized Repair Center to have it evaluated.

It could be some problem with Apple's kexts, but Apple will never figure that out unless people bring in their Macs for testing.

In the rare case it is something within NVRAM, try resetting it.

Here is how I suggest you do a clean install:

1) VERY IMPORTANT - BACKUP! You are about to erase your system drive. Never do that without a backup - well, actually, you should have at least two... I recommend a Time Machine on one drive, and a full clone of your system drive in a separate one.

2) Download the full  Big Sur installer from the App Store. If the installer starts automatically, quit it.

[if the OS you want to install is an older one, like Catalina, Mojave or High Sierra, use this link instead: https://support.apple.com/en-us/HT211683]

3) Create an installer drive on a thumb drive, following the instructions here:

How to create a bootable installer for macOS - Apple Supportsupport.apple.com › en-us

4) On recent macs, you may need to authorize booting from an external drive, which may be disabled by default. You do this in "Boot Security Utility".

Information about this is available in this support document:

https://support.apple.com/en-us/HT208198

---- do not proceed further without a backup!!!! ---- 

5) Restart your mac holding the Option key, and select that installer disk to boot your mac

6) Use Disk Utility to reformat your internal drive as APFS

7) Quit Disk Utility and start the installer. 

8) When asked, choose to migrate content from "another mac, time machine or drive".

IMPORTANT: elect to migrate ONLY user accounts; NOT applications, settings or other files

Yes, but how are we supposed to figure out what its cause may be? We need information to work on, and the easiest way to get it is by looking at the Etrecheck report that I asked for.

A kernel panic can have two types of causes: hardware failure or software. Without knowing anything about the mac in question and what software it has installed there is very little anyone can do.

Since you installed this creepy "cleanmymac" thing, you are going to have to erase and install. Like Barney said, there could be a hardware problem but any mac that has been tainted by cmm should have a clean install done.

I will post complete instructions for a clean install on a separate message.

How many disks do you have connected to your computer?

There is a known watchdog kernel panic with many disks. Generally 12 or more, but it can be less.

Watch your drives when you shutdown. They flush their cache Asynchronously, (one at a time), which depending on the drives, takes several seconds. If the amount of time flushing the cache takes more time than watchdog allocates, the system kernel panics.

this has been around for several years.

If this is your problem, then a simple fix is unmount your volumes first.

lecokey

This is what shows up after clicking on EtreCheck report found at, https://discussions.apple.com/content/attachment/f5238eca-80e8-4810-af56-ae3b0dce4f85.

Please use the "Additional Text" button below your message area, and post the full report:

Please run Etrecheck and post its report here. It will give us information about your mac hardware and software so we can look for common causes of issues.

I think lecokey has listed the problem he gets when shutting his iMac down and it fails afterwards though.

lecokey

When I click on report, I get to a website that doesn't work at all. Instead you need to give Luis Sequeira1 a report he can click on and get to easily afterwards.