In RadChart you have two options. First you can remove the XCategory ItemMapping. Depending on the scenario, this might not be a good option. The second suggestion I can make is to set the FieldName of the ItemMapping to correspond to some unique ID property.
In RadChartView when you have two items with the same category, they are being clustered. If this is not the desired effect, simply set the CategoryBinding to be the name of some unique ID property.
the Telerik team