This Crimson Waxcap might be confused with the Scarlet Waxcap (H. coccinea) for those who have not seen both. Usually it is a much bigger fungus and has a different colured cap (Crimson v Scarlet if that helps at all! I can only say it does not have the intense vivid colour of H. coccinea).

Apart from it's size (it is generally the biggest waxcap in Europe, although a small specimen might be confusing) and stocky coarsely fibrillose stipe, perhaps one distinguishing feature that is constant are the gills that tend to be narrowly adnate (hardly reach the stem) versus the Scarlet Waxcap where the gills are broadly adnate (fully reach the stem)

Another large Waxcap that might occur (it is known from California) is the Splendid Waxcap (H. splendidissima). Some people consider it a form of the Crimson Waxcap, and it's gills are also narrowly adnate. It has a deep scarlet colored cap rather than crimson, is very variable in shape but usually has a compressed twisted stem rather than the stocky stem of H. punicea. One important point is that it has a sweet honey smell, but not when fresh... only when it is drying