If we're talking about the fastest CPU in the world, that would be AMD's monster 64-core/128-thread Ryzen Threadripper Pro 5995WX, but that's a High-End Desktop (HEDT) processor. This means it's designed for serious content production like 3D rendering for movies or film scoring with dozens of digital instruments at a time - not the average consumer looking to build a PC. It's also hilariously expensive, with an MRSP of $6,499.
Bringing it back down to Earth, the fastest consumer desktop processor by benchmark scores is the Intel Core i9-12900K, hands down. But things get interesting when it comes to gaming. There, the AMD Ryzen 7 5800X3D absolutely crushes it, punching way above its weight and outperforming even the i9-12900K at 4K gameplay.