Keep a history of dice rolls per user and, if they don't pass a set threshold after so many rolls, adjust their rolls' results based on how you configure it.
Supported Systems & Dice
This module is system-agnostic.
It supports any dice roll from d2 to d100, rolling under or over the threshold, as you configure it.
How to Use
Go into the game settings and open the configuration menu to adjust the karma to your liking.
Simple Karma
If all of the previous N rolls didn't pass the threshold, the next roll will be rerolled its result reaches/passes the target number.
Average Karma
If the average of the previous N rolls didn't pass the threshold, the next rolls will be adjusted by the target number (e.g. +5) until the average passes the threshold.
The adjusment can be a fixed value (e.g. 5, 5, 5...) or cumulative (e.g. 5, 10, 15...).
Fudge
The rolls will be at least/most equal to the target value.
These can be set to deactivate automatically once they've been triggered, for cases where you really need a single roll to fail/succeed. Otherwise they will display a "circle of arrows" icon next to its name on the configuration menu.