bark is worse than one's bite

one's bark is worse than one's bite — "лает, но не кусает"; от него (от неё и т. д.) больше шума, чем вреда; больше шумит/ругается/кричит, чем на самом деле сердится;
ср. тж. great barkers are no biters; ~ собака лает — ветер носит.

Just as a dog may bark a lot but not bite at all, so we may say that a person’s threatening talk is worse than his actions will be

Example: Pay no attention to Dad. He looks mean and talks aggressively, he may sound threatening, but his bark is worse than his bite. Actually, deep at heart, he is a soft-hearted good guy, quite harmless and kind.