How do I delete duplicate Photos on iPhone 13 Pro Max?

Are you seeing these duplicates in the Duplicates folder in the Utilities section? There you can just select the version you don't want and tap the trash can.

Or you can choose "Merge." The Merge option picks the "better" of the images and adds it to albums that the other was in. In either case the trashed version is kept in Recently Deleted, giving you 30 days to change your mind.

Merge duplicate photos and videos on iPhone - Apple Support