The star in Orion with the largest radius is Betelgeuse. It's a red supergiant and is one of the largest stars known.

While the exact radius is still debated, it's estimated to be around 700-800 times the radius of our Sun.

Here's why Betelgeuse wins:

* Red Supergiant: These stars are known for their enormous sizes, due to their advanced evolutionary stage.

* Variable Star: Betelgeuse pulsates, changing its size and brightness over time.

Even though Betelgeuse is much larger than other Orion stars like Rigel, it's important to note that:

* Rigel is much hotter and brighter, making it appear brighter to us from Earth.

* Betelgeuse is nearing the end of its life, and could go supernova any time!