Brightest is a variable, there are up to 6000 lumen lights...comparing that to a car headlight at average of 700 - 1200 lumens.
The prices of these lights vary from the elite
Pro Niterider for 500 bucks to the casual
Lezyne 1300Macro for 100 bucks.
The Lezyne light is very bright and a great deal for the lumens. I recently got an
Outbound Lighting Headlight for $195 which produces 1800 lumens and has a cutoff for the light like a car headlight.
So it all depends on how much cash you are willing to fork. Be aware of the no name brands that claim “1xxx” lumens for 20 bucks, the lights never come near the lumen rating they claim and the battery life on these fail really quickly.
Thing is about headlights is that to be seen you need to be brighter than your surroundings and to feel safe is a priceless feeling. I had a cygolite before my ebike and that was fine, but once I am going speeds up to 28mph I need better headlights and price comes with that.