I am assuming that the Simple/Difficult/Borderline/Possible framework does not have actual impact on the roll and only serves as a guideline for how severe the consequences of a miss or partial success are.
For example if I were to take the fight between Naiki and the Burmese military in my own novel. She starts with an earthquake that lowers the land for about a hundred yards in every direction. Then she kicks an APC sending it end over end in one direction. So far she’s rolled well and not suffered any corruption or else only trace ignorable levels. Then she materializes her chi into a barrage of razor chi-discs, a feat she hasn’t trained to reliably do yet, and rolls poorly so even as she sends the discs to cut down some soldiers the blood vessels in her hands and upper arms burst causing bruising up from her fingers as the stress on her life force results in corruption that causes the physical symptoms. She then stomps her foot to the ground in order to create a spike of stone and tilt over the ogre main battle tank pelting her with 50 cal. Similar bruising and muscle tears spread up her leg as the tank is neutralized. Finally a soldier with an anti-tank weapon takes aim and sends out a rocket her way. At the last moment she raises a chi shield blocking the rocket entirely but the stress of raising such a powerful aura after stressing both her innate supernatural talents and her mother’s chi training causes a massive surge of corruption through her body sending her unconscious and slowly dying. And also serving as an object lesson why psychic/supernatural warriors generally fight at much lower than their maximum capabilities rather than sprint for one battle and being useless for anything that follows.
That sounds like several partial successes and misses using difficult or borderline skills ending with a lucky Last Chance roll which lets her get back in the fight later when she gets rescued by other characters and healing from her sister.
Also. Is it possible to spend achievements to move something from borderline to difficult as a character trains to be more efficient with their powers?
As an example. Naiki’s mother could easily summon multiple chi discs with no problem despite having lower innate levels of chi than her daughter. Long training has made her able to have more effect with less effort.
Yeah, you’ve got it down. The differences in Powers Profile levels has more to do with consequences and/or what needs to happen in the fiction before the hero can pull them off rather than anything to do with the roll itself.
I’m pretty sure Achievement points can be spent to do some stuff with powers but I don’t have the book or my computer near to double check. At the very least something like that was in there but it might have gotten removed last minute – i really can’t remember. I think that’s a totally legit way of using Achievement Points though, for sure.