lack of balls
A weakling who rants about you like you're the devil but hides in a closet when you come for them.
My neighbor said I was a mess to the mailman, but when I showed up at his door, he acted like he was just cleaning his house.
My sister said I was a disgrace in the kitchen, but when I walked in, she was too busy eating her snack to notice.
My teacher said I was a nightmare in front of my friends, but when I showed up, she was too busy grading papers to care.