If one axis of the story alignment chart describes the moral quality of the universe the protagonists find themselves in, represented as a sliding scale of bleakness (or utopia, although bleakness is mentioned here because if everything was wonderful there’d be no tension and hence no story) the other represents the power the protagonist themself has to change the world. Sometimes the protagonist is so powerful as to unbalance the story. At the other extreme is a character who is so insignificant in relation to their universe as to have no power to do anything important at all
Mary Sue / Gary Stu – The over-powered protagonist is called the Mary Sue. A Mary Sue is far more powerful than the universe they are in, and the other characters in that universe. Originally appearing in fan fiction, the Mary Sue is an idealized and seemingly perfect fictional character, who is so competent and perfect as to out-perform all the other characters in skill and intelligence. At the very least they can usually perform better at tasks than should be possible given the amount of training or experience. They may also be more attractive or for some other reason liked by everyone. Often, such a character is recognized as crude author wish fulfillment, and in any case is an example of bad writing]
Despite the name, Mary Sues don’t have to be female. A male Mary Sue may be called the Marty Stu or Gary Stu. Two classic mary sues are Wesley Crusher of Star Trek The Next Generation, and Rey of the Disney rebooted Star Wars sequels.. There is however a lot of argument over whether a character is a Mary Sue or not. This is the case even in the above two examples.
Hero. Like the Mary Sue, the heroic character is able to achieve great deeds and even help save the world or galaxy. But they differ in being more balanced and less super-powerful in relation to other characters and the universe they feature in, with various flaws and weaknesses, and facing great challenges and, in the case of a crapsack or bleak world, great sacrifices. In the Story Alignment Chart, the Hero is a feature of a Bright-Noble or Dark-Noble story.
The placement of a character on this scale is rather arbitrary. For example, teenage Katniss Everdeen is the central personality in overthrow the oppressive rule of the Capital in Hunger Games. And whilst this can be understood as a metaphor of teenagers coming of age and overthrowing parental restrictions to become their own person, in terms of realistic worldbuilding it makes little sense, and even feels somewhat Mary Sue-ish, although it could be argued that the character is more balanced.
Influential character. The Influential character is not at the level of a Hero, but can still get by in their world or universe. They can change their own life, but unlike the Hero they can’t change their universe. Despite their personal achievements and victories, the world continues as it always was. Most superheros for example belong in this category. After beating supervillains, the world remains the same, until the rise of the next supervillain. In story alignment, this is the neutral world, between noble and grim.
Powerless character. A powerless character can’t even improve their world in small ways. At best they just get by. If they live in a bleak world/universe, they may be executed or imprisoned at any time. Their situation is pretty grim. However, they can at least improve their life in small ways.
Mook. The mook is totally helpless against the forces or dramatic devices arrayed against them. They can’t even manage their life in the way an otherwise powerless protagonist can. Usually they just end up as cannon fodder, as for example the hapless bumbling, expendable stormtroopers of the Star Wars universe. The word mook is used in TV Tropes to refer to the useless cannon fodder of the Bond supervillian or evil emperor. As used here, mooks don’t have to be minions of villains; they are just anyone who is so overpowered by their circumstances that nothing they do makes the slightest change. For example, Winston Smith in 1984, or humanity as a whole in Lovecraft’s Cthulhu mythos.