The iPhone 13 Pro Max can charge a bit faster than other models, according to tests done by YouTuber ChargerLAB (and backed up by other tests), which show that the phone sips up to 27 watts of power when plugged into a compatible charging brick. If you have a 13 Pro Max and want to fill up its massive battery as fast as possible, you may want to look into getting a 30W charger that, according to tests cited by @duanrui1205, can charge it from zero to full in less than 90 minutes.
This appears to be an upgrade from the previous generation — 9to5Mac reports that the iPhone 12 caps out at around 22W charging speeds. That’s about a 5W boost, which is nothing to sneeze at. The benefit of a bigger charger is limited to the Pro Max, according to @duanrui1205, who said that the smaller iPhone 13 Pro could only charge at 20W. All of this goes out the window if you’re charging wirelessly or with Apple’s MagSafe puck — you’ll be limited to 15W at most.
If you’re looking for a 30W brick to charge your Pro Max a bit faster, it’s probably worth looking around your house first: Apple includes 30W chargers with its new MacBook Air, and the 61W charger that comes with MacBook Pros could also provide the 27 watts your phone craves. You can check any other chargers in your house by reading the regulatory text that’s usually printed near the prongs — if it doesn’t outright say the wattage, you can figure it out by multiplying the amps and voltage.
If your search for a 30W charger didn’t turn up anything, Apple will happily sell you one. You can also find plenty of third-party ones, like Anker’s tiny Nano II GaN brick. One thing to note when looking at chargers is the charge rates they support — to get the 27W charging, the iPhone is looking for 9V at three amps, according to ChargerLAB’s video (which shows one 30W charger that’s only charging the iPhone at 18W).