Karma, as a spiritual concept derived from ancient Hindu, is often misunderstood and distorted by the new age community and others in the West. So let's begin by first debunking what karma is not.
It is not punishment per se, although it is the logical consequence that follows from thoughts and deeds. It is not necessarily negative, although it can be harsh and seemingly undeserved if the causal action or hurtful speech occurred so long ago, or even in a past life, that the conscious mind has forgotten the seed that became the bitter fruit.
By the way, as far as I have been able to research, the concept of karma does not have an identifying symbol associated with it. However, because of the potential for being either positive or negative, perhaps what is called the yin /y