Machiavellianism
A sneaky person who lies, cheats, and steals just to look good and get ahead.
Your mom said she'd give you $20 if you did your chores, but it turned out she only had $5.
Your crush said they'd go to the movies with you if you asked, but then blocked you on Instagram.
Your friend said they'd help you with your math homework, but they just copied your answers.