The ~25% chance of success wasn’t in FIST, I was referencing to the OSR style games that Claymore referenced where you need to roll a 15+ on a D20.
But I admittedly do struggle with the partial successes. I’m not good at figuring out what a ‘complication’ should be necessarily. Sometimes I can’t think of a complication related to the roll that feels appropriate without making it an effective failure.
Like, one of my players was trying to sneak up a ladder while a person nearby it was distracted. Rolled a partial success. What do I do there? I had one of the rungs on the ladder snap underfoot when they reached the top of the ladder, alerting the guy at the top and bottom of it, but giving them time to react before being seen.
This felt like “Success with a complication” to me but “Failure” to them.