Gaining a Low Investment High Damage Unarmed Strike

[SangoProduction]

Depends on what you consider an "investment," and if you consider "high damage" and if you consider rider damage effects to count as "Unarmed Strike."

But for a 1 level dip in the Champion of the Spheres class, Sage, you get to add 1d6 points of damage to your unarmed strike, and can spend a martial talent on an unarmed-styled sphere to gain Improved Unarmed Strike.
So now you're doing 1d6 + 1d4 (base unarmed) damage at level 1. That's 1 less average damage than a greatsword. Or in other words, almost the equivalent of a 15th level monk at level 1.

You can add 1d6 per odd level in the class. So by level 3, you're essentially the equivalent of an epic level monk. (Yes, I am comparing it to monk damage to inflate the relative value. Thanks for noticing.)

Also, Sage can come equipped with touch-targeting Unarmed Strikes, +10 to Strength, and more damage boosts, as you can read about here.