IMAC running super slow and eventually it stopped, so wiped it and reinstalled OS....it works, but still slow.

I have some useful comments to share. Fusion drives can be problematic since they can split, which mean that you are no longer using the faster SSD portion and the computer is running off the much slower mechanical drive. I suggest you do the following.

• Purchase and connect an external SD . Be sure to get one that has sufficient storage to accept all of your computer's data. It can be easily connected using a vendor provided USB cable.
• Before using, reformat the disk using Apple's Disk Utility app. Do not use any maintenance apps which may come with the disk. They always cause problems and should be deleted.
• download and install an operating system on the SSD.
• Begin the process of setting up the OS. At some point you will be asked if you wish to transfer your data. Click yes and use Migration Assistant to do so.
• Note - you can only transfer all or none of your installed apps and data.
• The process to do the transfer may take up to 45 minutes or so.
• When completed, the new disk should have been set up as the new startup disk.

You will now expense a much faster operation of the computer.

The 2T HDD part of the Fusion Drive is normally the first to fail.

To dig into that deeper, use > https://binaryfruit.com/drivedx

If the 2T HDD is failing then you have a couple of options...?

1) Have the failing HDD replaced by your local AASP.

see > https://getsupport.apple.com/repair-locations?locale=en_US

2) Startup and run the iMac from an External SSD.

see > Use an external SSD as your startup disk … - Apple Community

Hi Ron, according to diddles1911's EtreCheckPro report.

The Fusion Drive is currently fused and erased, but still preforming slow.

So... any migration or transfer will have to come from Time Machine or another backup.

Anyhow.... good work and an Upvote from me.