Ranks and Crossover Worlds:
F - Average humans.
E - Athletic Level humans.
D: Street Level: stands at the threshold of human strength and capabilities, represented by Olympic-level athletes.
C: Wall Level: characters that can destroy or significantly damage extremely resistant materials such as stone, metal or steel.
B: Small building level: characters capable of destroying rooms or entire small constructions such as houses or more modest buildings.
A: Building level: characters that can destroy medium-sized buildings and constructions.
S: Large Size Building level: Characters that can destroy large buildings such as skyscrapers.
SS: City block level: Characters that can destroy urban city blocks or equivalent areas of space.
SSS: Multiple city block level: Characters that can destroy multiple urban city blocks or equivalent areas of space.
Ex: City level ( 10-100 times stronger than SSS Ranks)
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Every Rank is further divided into three stages. Example: (A-) (A) (A+)
Note: It is an estimated assumption according to destructiveness capability but It may vary according to a person's Skills and how he utilizes them.
Crossover Worlds:
The Bully In Charge
Mercenary Enrollment
Lookism
Boss in School
Baki
The Descent of Demonic Master
Weekly Power Status
-- Power
Ranking 
-- Power
stone