General Antonyms:
* Honest
* Straightforward
* Naive
* Innocent
* Open
* Forthright
* Sincere
* Trustworthy
Antonyms focused on lack of skill:
* Clumsy
* Inept
* Unskilled
* Naive
Antonyms focused on lack of deception:
* Frank
* Candid
* Genuine
* Open
The best antonym will depend on the specific situation and how you are using the word "cunning."