An alternative to deleting is to merge two labels. For example, suppose your helpdesk has two versions of a label, one correct and one misspelled.
Deleting the incorrect version would lose the information about which tickets it had been applied to. A better alternative is to merge both versions.
Click on the incorrect version, edit the label text so it’s exactly the same as the correct version, then click Save.
All the tickets with either label are now labelled with the correct version: