Custom Button Redirects Sensibly To List View

   public PageReference deleteAll() {

        // Delete all records here.
        list<CalloutConcentrator__c> allRecs =  [select id from CalloutConcentrator__c];
        delete allRecs;

        // Redirect to the List View.
        Schema.DescribeSObjectResult anySObjectSchema = CalloutConcentrator__c.SObjectType.getDescribe();
        String objectIdPrefix = anySObjectSchema.getKeyPrefix();
        PageReference pageReference = new PageReference('/'+objectIdPrefix+'/o');
        pageReference.setRedirect(true);
        return pageReference;
    }

The button configuration:

It’s a LIST BUTTON.

Behavior: Display in existing window without sidebar or header

Content Source: URL

https://YourOrg.visual.force.com/apex/CalloutConcentratorDeleteAll

<apex:page controller="CalloutConcentratorController" action="{!deleteAll}">
</apex:page>