cringe and smile obsequiously; bow and scrape; flatter sb. shrugging one's shoulders and smiling; flatter sb., with hunched shoulders and a smiling face; shrug one's shoulders and offer an ingratiating smile; try to win sb.'s favor by servile behavior; smile like a sycophant:
He was the kind of person who would flatter you to your face, and then slander you behind your back.