These six adjectives describe ability, but they emphasize different things. They overlap, so they do not form a fixed ladder from weakest to strongest.
- Capable focuses on having the ability to do something, even if you have not done it yet. I think Leo is capable of leading the team. It can also describe someone who handles responsibilities well.
- Competent means having enough skill and knowledge to do something properly. We need a competent accountant to check these records. It usually suggests reliable performance, not exceptional talent.
- Skilled emphasizes ability developed through training or practice. A skilled mechanic identified the fault immediately. Use it for practical, professional or creative abilities.
- Proficient means able to do something well, especially a particular activity. Applicants should be proficient in Excel. It is common in descriptions of language ability and workplace skills.
- Accomplished suggests highly developed skill supported by achievement, especially in the arts. Her father is an accomplished violinist. It sounds more admiring than simply saying someone meets the required standard.
- Expert emphasizes very high skill or deep knowledge in a particular field. We asked for expert advice on restoring the painting. It does not imply knowing everything.
Notice the patterns: capable of doing, skilled at doing and proficient in something. Choose the word that matches what you want to highlight, rather than treating every description of ability as a score.