Peace treaty refusals:

[Castellon]

It is defiantly worth going for 100%. However both at 100% and any other score, If the AI has allies, Troops, or ships. It will refuse to accept the "close to war score" peace deals.
So the lesson we can take from this is to crush their allies, get 100%, kill all troops and ships, Then start the peace process.

 

[Castellon]

Originally posted by Wyvern
I think DPS is right though in his conclusion that you need a high upper limit on your war score before -1 stab hits start to take place. I've never been able to generate a stab hit on the enemy when my war score was below about 40% even when I ask for virtually nothing. Above 70% and it's very easy to do even with a small differential.

Well it would make sense that it had to be greater than 50%.
Since you should not be penalized for not accepting peace when the war has not been decided.