Open the Photos app
Tap Library or Albums
Select the photo or photos you want to delete
Tap the Trash icon
Tap Delete Photo or Delete [number] Photos
Open Albums
Scroll down to Recently Deleted
Tap Select
Tap Delete All or choose photos and tap Delete
Confirm deletion
To erase photos from iPhone storage, turn off iCloud Photos only if you want them removed from all devices first
To delete photos from a specific album, remove them from that album or delete them from the main library
To delete photos from Messages, open the conversation, press and hold the image, then tap Delete
To delete photos from Files, open Files, select the image, and tap Delete
To permanently remove photos, clear them from Recently Deleted as well