Apple

Apps in the Apple iTunes Store can only be deleted under certain conditions.

1) The app must have at least one approved version available in the store.

2) The latest version must be assigned a specific status. This includes:

Prepare for Submission
invalid binary
Developer Rejected
Rejected
Metadata Rejected
Developer Removed From Sale
Removed from Sale

If the current version has a different status, it must either be removed from sale or build rejected.

3) The person who wants to remove it must be assigned the Team Agent role.

If the above conditions are met, the button "Remove/Delete App" will appear on the App Information page.

Google

In Google Play, apps can no longer be deleted once they are published. The only option is to stop publishing the app. You can do this by going to the app in the Developer Console and clicking on "unpublish" next to the app name. Then the app will no longer be available for sale in the store.