What's the fastest way to find and delete duplicate nodes inside XML?

XML file has structure like this

<Nodes>
   <Node> one </Node>
   <Node> two </Node>
   <Node> three </Node>
   <Node> three </Node>
</Nodes>

Since xml file has more than 30000 nodes I'm looking for fastest way to find and delete duplicate nodes.

How would you do it?