There’s a way to bulk delete photos in Flickr, but it’s not very obvious. But once you know, you know. Here’s how.
After you login to Flickr, go to https://www.flickr.com/photos/organize/ and that gets you to the Batch Organize feature.
Then you can select photos to “Drag items here” to edit as a batch.
Select the menu item Edit Photos under the Flickr logo, select Delete.
Finally, just confirm the permanent delete. Are you sure? There’s no turning back.
Voila. That’s all.