Open Google Photos on your phone or go to photos.google.com on a browser
Sign in to the Google account you want to clean up
Select photos and videos you want to delete
On mobile, tap and hold a photo, then tap more items to select multiple
On web, click the first item, then hold Shift to select a range or use Ctrl/Command to select multiple
Click or tap the trash can icon
Confirm the deletion
Open the Trash or Bin folder
Click or tap Empty trash or Delete forever
Confirm again to permanently remove the items
Repeat the selection and deletion process until all photos and videos are removed
If you want to delete everything faster, use Google Takeout only if you need a backup before deleting
Check that Backup is turned off in Google Photos if you do not want deleted items to reappear from synced devices
Delete photos from any connected device or cloud backup source if needed