It's tricky to say definitively which is the "biggest" planet discovered, as there are different ways to measure size:

* By diameter: HD 100546 b is currently considered the largest exoplanet discovered, with a diameter about 6.9 times that of Jupiter.

* By mass: DENIS-0255-4700 b is the most massive exoplanet discovered, with a mass about 28 times that of Jupiter.

However, it's important to remember that:

* We're constantly discovering new exoplanets: The field of exoplanet research is rapidly evolving, so it's possible that even bigger planets will be found in the future.

* Measurement uncertainties exist: It's difficult to determine the exact size and mass of exoplanets due to their distance and indirect observation methods.

So, while HD 100546 b currently holds the record for diameter, and DENIS-0255-4700 b holds the record for mass, this could change as new discoveries are made.