Once again, simply don't exploit the system.

I can savage any faction on the map, rape their land and bully them for 50 years, then give them a 10,000 state gift (which isn't even a scratch on my treasury) and all of a sudden they're my best buddies, calling me every day asking if i want to go for a beer and telling me i should date their queen.

That's an exploit. I shouldn't be able to rape a nation hardcore and then give them 10,000 and make them my best friends, so you know what? I don't.

I also don't trade with everybody i can. I don't trade with nations who are trading with my enemies. I don't steamroll my enemies or my economy. I don't keep more than one school. I pick my wars carefully and always fight slowly and steadily.

Do all this, and you'll get your challenge.