General Description: The ability to lift and put force through the human body well beyond that of the norm that humans are capable of, turning punches and kicks into deadly lethal, heavy objects into throwing weapons, and more. Bending steel, breaking wood, and smashing stone becomes easy over time. The upper limits vary, but are none the less terrifying to see in action when a normal human being smashes through stone with their hands alone. It comes with a cost, however, in that the user of the ability finds they now exist in a world that is all too delicate and breakable, like a world made of paper and cardboard, which cause them to have to re-learn the right amount of force and gripping strength to avoid breaking things... and people.
D-Rank: The user has immense strength and no finite control over how much gripping strength and force they end up using with the capability to very easily lift and throw a grown human male or smash through a wooden door. While they might not always destroy everything they touch, it becomes more common - especially during emotional extremes such as rage, excitement, or sadness which can cause them to very easily break things, hurt, or kill people. It's fairly common for users at this stage to break glasses in their hands, pull doors off of hinges, break vehicles without meaning to, and otherwise damage people and property whether they mean to or not, often causing the emotional duress to become worse. The upper limits of their strength is unknown. They will also be able to begin "leaping" using the strength in their legs, launching themselves through the air and landing, although may not be particularly good at this for some time, and it can actually be damaging. Users at this stage can experience muscle strain by pushing themselves too far, which is only compounded and amplified depending on how much they attempt to push themselves, to the point they can begin tearing muscles and ligaments. It is entirely possible to accidentally kill a normal human at this state during an emotional extreme.
C-Rank: The user becomes more capable of controlling their force and grip strength but has to do it through conscious effort, though still needs to take care as they've yet to come close to fully mastering it, and they might still break things or people unintentionally if they do not actively take care not to, or do things reflexively. The upper limits of their strength is presently unknown still, but they begin to be able to break through stone walls and lift small vehicles like motorcycles. Straining and damaging ones self becomes slightly less of a concern as the body begins to condition itself towards the new exertion.
B-Rank: The user has full control over finite force and grip strength and will rarely unintentionally destroy an object or injure a person unless caught off guard or experiencing immense emotional duress. At this stage, users can begin to explore their upper limits in a more consistent manner given the level of control that they have have, beginning to reach a point that they can lift cars and throw themselves through concrete with minimal effort with focused applications of their strength without causing too much wanton destruction; unless they want to, at least. Strength-leaping becomes easier, as they have more control over themselves, and they can begin to use this to cover ground with relative ease if needed or leap to the top of small buildings, leaping is no longer damaging so long as the user does not leap off of tall buildings, and muscle strain begins to decrease.
A-Rank: The user has mastered the control needed to function almost entirely normally with their strength and conditioned their mind to subconsciously apply just what is needed and will almost never slip up. Users at this stage have almost full control over themselves and exactly the sort of strength in which they can apply, with the upper limits expanding well beyond what they previously might have thought them to be, able to lift busses and leap to the top of larger buildings. Their body becomes a lethal weapon in close combat if they so desire, or they can apply exactly the right force they need to break bones or knock a person unconscious. Muscle strain is near non-existent but still entirely possible if the user goes much too far past their own growing limits.
S-Rank: Casual, complete control. Those who reach this point are able to commit feats of strength entirely casually of lifting large vehicles with one hand, leap to the top of skyscrapers with a single bound, and even could lift large buildings. Muscle strain is no longer a concern, at all.