Google play has introduced ability to delete apps published in play store.

Requirements for apps :-
Should have less than 100 installs at that time.
Should be a free app
Shouldn't be a suspended or removed app

App deleting can be done by owner account only

Steps->
Go to app-> advanced settings -> set to unpublished -> delete option will appear -> click delete and enter 25$ payment transaction id and app's package name-> in next dialog enter "delete"
And done your app will be deleted in next 7 days