Summarize the following:
If you store your contacts in your Google account, you can use Google Contacts to manage them more efficiently. This can be done from the Google Contacts website. This will only work for contacts stored in your Google account. Contacts stored on your phone or from another account will need to be deleted separately. Log in with the same account you use on your Android device. The Search bar at the top of the page can help you quickly find the contacts you're looking for. This will delete all of the selected contacts from your Google account. If the trashcan is grayed out, one or more of your selected contacts were added through Google+. You'll need to remove them from your Google+ circles to delete them. See Create Circles in Google+ for details. After removing the contacts from the Google Contacts website, you'll need to resync your account on your Android. This can be found in the Personal section. If you have multiple Google accounts, you'll be prompted to select the one you want to modify. You'll find this in the upper-right corner. Your Google account will resync your Google data, including your contacts. Any contacts that you deleted on the Google Contacts website will be removed from your Android device.

Summary:
Open your web browser. Enter contacts.google.com in your browser. Tap or click the contacts' profile pictures to select them. Tap or click the trashcan button at the top of the screen. Tap the Settings app on your Android. Tap Accounts. Tap Google. Tap the ⋮ button. Tap Sync now.