Actions speak louder than words. What characters do can say a lot about them, for good and ... not so good. This trope will make us dislike characters before we really have the chance to get to know them.
Kick The Dog - used to immediately identity a character that we're not supposed to like, often through petty misdeeds or unforgivable acts. This trope has no purpose but to label a character as "bad" to the audience upon introduction.
This trope is the polar opposite of Save The Cat.
This is not limited to kicking dogs - it can be any cruel action, unkind remark, or abuse. The world is full of examples, more than we can account for. Just about every story has them and the possibilities are endless. Doing so gives the audience an emotional reaction and suspicion, a great tension building tool. Even the little balloon animal in this example happens to be a dog!
Have you ever kicked a dog? ... In your story, of course. What Kick The Dog moments have you seen?
I'm David, and don't throw off the emperor's groove ...