Deleting agents can mean simply deleting an agent from the agent list on the Agents page, or it could mean removing an agent from the cluster permanently. Unless agent hardware was physically disconnected, or the agent service was stopped, agents reappear in the agent list (because connected agents are automatically detected).
On the Agents page, click the Delete Agent link in the Action column for the agent you want to delete. This action removes the agent from the database.
On the Agent Details page, click Delete Agent to delete that displayed agent.
Go to the Filter drop-down menu and select a filter.
Click Run Filter.
Click Delete Filtered Agents.
From the Filter menu, select none, then click Run Filter.
This removes the agents from the database.