my unique skill makes me op even at level

They could start off not fully understanding their skill. As the story progresses, they learn more about its limits and potential. For example, if the skill is teleportation, at first they might only be able to teleport short distances, but later they figure out how to cross vast distances.

Yes, it could. If the unique skill gives you a significant advantage over others in the manga's world, it might make you OP.

Maybe the protagonist has a skill like super speed which allows them to outrun any enemy or complete tasks impossibly fast, making them seem overpowered (op).

In terms of an employee's work task, the skill level referred to a work task unit or a work function that the employee had to perform in order to complete the work task. In terms of professional skills, employers, professional colleges, and social training evaluation organizations selected and announced by the human resources and social protection departments would assess and evaluate the professional skills of workers according to national professional standards or evaluation norms. This activity was called professional skill level recognition. Professional skill levels were generally divided into five levels: junior worker (level five), intermediate worker (level four), senior worker (level three), technician (level two), and senior technician (level one). The employer could further divide the levels according to their own needs, or set up special technicians, chief technicians, etc. The social training evaluation organization generally carried out the evaluation according to these five skill levels. The occupations (types of work) recognized by the professional skill level are the skill-based occupations (types of work) in the current "Professional classification of the People's Republic of China" and the skill-based occupations (types of work) issued or filed by the Ministry of Human Resources and social protection. The national professional standards were organized and formulated by the Ministry of Human Resources and social protection. The industry enterprise evaluation standards were developed by the employer with reference to relevant regulations and implemented after being filed by the Ministry of Human Resources and social protection. Different types of skilled talents had different work characteristics, so they were evaluated according to categories. For example, for technical and skilled talents, they should highlight the requirements of practical operation ability and solving key production technical problems; for knowledge and skilled talents, they should highlight the requirements of mastering and using theoretical knowledge to guide production practice and carry out work in a creative way; for compound skilled talents, they should highlight the requirements of mastering multiple skills and engaging in complex work of multiple types of work and multiple posts. The evaluation agency would determine the evaluation content and evaluation method according to the national professional standards or evaluation norms, and comprehensively use a variety of evaluation methods to conduct a scientific, objective and fair evaluation of the worker's professional skill level. The professional skill level certificate shall be issued by the employer and social training evaluation organization registered by the Human Resources and social protection Department after the professional skill assessment and evaluation of the laborer within the scope of the registered occupation (type of work). The certificate shall be independently printed and issued by the evaluation organization. The government department shall not participate in the supervision. The certificate shall be valid for life, universal throughout the country, recognized by the state and society, and available on the national network.(The inquiry website is the technical talent evaluation website designated by the Ministry of Human Resources and Social Security.)

In Fairy Slaying Dream, the upgrade of a mythical beast's skills usually added a skill. These skills were usually the special abilities of the mythical beast itself, which could improve the attack and defense ability of the mythical beast. The process of leveling up a Divine Beast skill required a large amount of experience and gold coins, and there was a certain degree of risk because the Divine Beast might become more powerful after leveling up, resulting in an increase in the difficulty of the challenge.