* Deceptive: This is a general term that accurately reflects Marty's actions of misleading others.
* Dishonest: This is a stronger term that implies a lack of integrity and moral compass.
* Untruthful: This focuses on the specific act of telling lies, without necessarily implying ill intent.
* Manipulative: This suggests that Marty uses lies to control others or get what he wants.
The most appropriate word depends on your specific interpretation of Marty's motivations and the overall message of the story. For example, if you believe Marty lies out of fear or insecurity, "deceptive" might be the best fit. If you think he lies intentionally to get what he wants, "manipulative" might be more appropriate.