A person who pretends to have more knowledge or skill than he really has

One word substitute is Charlatan.

Renegade: a person who deserts and betrays an organization, country, or set of principles.
Apostle: each of the twelve chief disciples of Jesus Christ.
Charlatan: a person falsely claiming to have a special knowledge or skill.
Apotheosis: the highest point in the development of something; a culmination or climax.