Just look for the shadow version of the weapon you want.
You can buy the best version of each weapon from any of the mid- to late-game merchants (usually the ones near or in Meridian).
You’ll have to do some work to get it, but it is very, very worth the trouble. There are a lot of useful outfits that you’ll pick up, each with their own useful situations - ice hunter armor is good to wear while fighting glinthawks, for example - but there is one outfit that stands apart from the rest. The best outfit is a much different situation. We’ll focus on those in the best weapons section. Each has its uses and its strengths, but there is no single weapon that we’d call “the best.” There are better versions of each weapon, though, and a few unique weapons.
Before we even begin, let’s clarify something: There is no single “best weapon” in Horizon Zero Dawn.
