The symbol in general can mean many things: past, present, future; mother, father child; or alpha, beta, omega. For werewovles, it symbolizes that possibility that any wolf can rise or fall to any status. A beta can become an alpha. An alpha can fall all the way to an omega.
The revenge spiral is a simple spiral consisting of any number of revolutions. It signifies that there is a blood debt to be paid. Derek buried Laura under a spiral of rope attached to wolfsbane, which kept her from shifting and signified his intent to kill whoever killed her. Peter Hale drew the spiral in a number of places to signify that he was meting out justice to those who killed his family.