Vengefulness is a strong desire to get back at someone for something they did to you. Your vengefulness toward that kid who taped a "kick me" sign on your back is totally understandable.
Have you ever longed to get revenge on someone? Then you've experienced vengefulness, an urge to retaliate for bad or unfair treatment. Both vengefulness and revenge come from a verb we don't use anymore, venge, which meant "to take revenge or punish." History and literature are both brimming with stories of vengefulness, from Hamlet to Homer's Iliad to The Princess Bride — everyone's out for revenge.