You can, of course, delete a release too using the helm delete command.

First, let's examine the list of releases. We have only cranky-whippet:

> helm list
NAME            REVISION     STATUS      CHART           NAMESPACE
cranky-whippet    5         DEPLOYED   mariadb-2.1.3      default  

Now, let's delete it:

> helm delete cranky-whippet 
release "cranky-whippet" deleted 

So, no more releases:

> helm list 

However, Helm keeps track of deleted releases too. You can see them using the --all flag:

> helm list --all
NAME                 REVISION  STATUS    CHART          NAMESPACE
cranky-whippet        5        DELETED   mariadb-2.1.3  default 

To delete a release completely, add the --purge flag:

> helm delete --purge cranky-whippet