The opposite of genuine is: SPECIOUS
According to Google this are the definitions for the following words.
Genuine: honest, authentic
Solicitude: caring for something or someone
Specious: misleading in appearance, fake
Abrogated: evading, getting away with something
Cursory: hasty, not detailed
Superlative: a high comparison
Vitiate: to spoil the quality of something
Bugbear: scary being like a hobgoblin
Propensity: tendency towards something
Insipid: lacking flavor
Therefore, the opposite of honest and authentic would be fake or misleading in appearance
