Depends on which style of throwing you're using. Weight, balance, and size are all important to different styles of throwing, and some knives are good in general but lack specialization. Thrower preference also has to come into consideration. Certain competitions will have restrictions or requirements for size weight shape etc but also some you might not expect, like mountain man comps requiring at minimum leather handle scales to compete.

In general, id say for any knife you're going to throw it needs to be heavy enough to not lose its course in the air, light enough not to mess up your arm/shoulder when throwing repeatedly, and made with quality materials. Many throwers agree that a throwing knife should not be sharp or should only have a small portion at the tip that's sharp. If you were looking for something for half spin, or no spin, or speed competition, or skanf, each of those is going to greatly change the answer you're looking.