//remove all labels on chart
foreach (DataPoint item in chart1.Series[0].Points)
{
item.Label = "";
}
//alternatively disable all labels
chart1.Series[0].IsValueShownAsLabel == false
Now add label to last point. You could pick any Chart1.Series[0].Points[i]
to put the label on, but in this example it adds the label to the last point
_Point Point = chart1.Series[0].Points[chart1.Series[0].Points.Count - 1];
_Point.Label = chart1.Series[0].Name;