Remove contact card from list in Contacts on iMac

If you are using the Apple wireless keyboard then it definitely has a Delete Key, please check again. You can also use the menu:

Edit - Delete Cards and follow the on-screen command. You can also create a keyboard shortcut for this action.

Also, when I asked Google how to remove a card from a list it replied:

"Open the Contacts app and select the card(s), right click or two finger tap and choose Delete Card or just choose the Delete Key"

LordGnome100 wrote:

Sadly, that doesn't want to work, either. If I right click on the card it doesn't offer a 'delete' option.

If I right-click on an entry in the LIST column of contacts, I get a "delete card" option:

That's in macOS Tahoe on an M4 Pro Macbook Pro but worked the same on my old iMac running macOS 10.14 Mojave.

See if the information in this support article guides you: Delete lists and Smart Lists in Contacts on Mac - Apple Support

Right click on the name and pick delete. Is the key in the upper right with the "x" the delete key?

To me it looks like the delete key is the second one down on the right in your picture. Above the Return key with the curved arrow. My forward delete key has that icon but pointing to the right.