Macro Deletes all rows except....

Try

Sub DeleteUnwanted()
    Const TextToKeep As String = "DELV" '<-- Change to suit
    
    Application.ScreenUpdating = False
    With Range("C1", Range("C" & Rows.Count).End(xlUp))
        .AutoFilter Field:=1, Criteria1:="<>" & TextToKeep & "*"
        .Offset(1).EntireRow.Delete
        .AutoFilter
    End With
    Application.ScreenUpdating = True
End Sub