From top of my head:

File renaming. What Forklift or other dedicated file renamer comes as a standard with both Dolphin and KRename. Latter can drive circles around what's available in macOS, in any form.

AudioCD ripping: kio:// protocol has a native ripper. Just drag and drop. Settings are integrated to system settings directly. Which format do you want? Yes.

Remote connections: While finder can connect to servers, but FTP read access and SFTP requires external apps. IOW, what Cyberduck provides is already available in Dolphin, again.

KDE's standard window management capabilities need Magnet or something more advanced in macOS.

Git/SVN/CVS needs external tools in macOS. Dolphin can detect these repositories and let you work on them on the spot.

KRunner is arguably more Capable than spotlight in some cases. Needs another fair shake though.

If you add your mail accounts and calendars to KDE via KMail or something else, they become available system-wide. macOS is good in that regard, but KDE is betterer. If you use KMail, your mail will sync at the background even though your mail client is not running.

You need to buy another application to be able to edit id3 tags of audio files, but KDE has kid3. I even use its macOS version because it's that good.

I'll not get into customization capabilities, because they are fundamentally different and worlds apart, but this is due to their philosophy.

Keyboard shortcut management are equally powerful in both, AFAICS. macOS used to lag there.

K3b is infinitely more capable than macOS optical media authoring tools.

These are what I can remember with my tired brain, away from my KDE system for the day. The thing is, both side by side, I mostly prefer KDE because I can work way faster on that one, and it's not I'm hating macOS or anything, and as I said, using both for a very long time.

The apps I have given as examples are KDE's default apps and maintained by KDE project themselves. They are part of the default installation.