The lust for revenge can be a principal driving force in a person’s life. What is the belief behind that drive, and where does it come from?

This we would say is further on the continuum in terms of "the strength of hatred," so we would say having "a lust for revenge" ranks below being "consumed by hatred" on a downward spiral of negativity. This is the temptation the evildoers surrender to; because they cannot hold lofty thoughts, they cannot experience love to feel its rewards or offer it to others as a way of raising their own vibration. Their only enjoyment in life can be experienced as gaining something at the expense of another. This is getting into the territory of the narcissist and the sociopath who are devoid of compassion and the ability to love, to a large or extreme extent, as the case may be. A lust for revenge is a self-indulgence in depravity and is a low perspective indeed, that one would feel satisfied only by causing an equal or even greater harm to a perceived foe as a solution to their inner drive for revenge. The reason this is so harmful is that it is a drive to, in effect, become equal to their perpetrator as a source of negativity and power directed at causing harm. So harboring such thoughts and yearnings and making it a high priority, or even a life goal, is stepping into the shoes of the perpetrator without a conscience and seeking harm to others without any thought to the consequences, in a longer-term sense, and such a person may be digging their own grave—causing severe harm to others or to the self may, in fact, be resolved through the Law of Karma by having a future lifetime greatly shortened in repayment of the pain and suffering they have caused to indulge their lust for revenge. The fact that the books are always balanced by the Law of Karma guarantees if they harm another, they will harm themselves in parallel and often to a greater degree because all of the consequences of the harm caused beyond their target to those who depend and care about them, who will be hurt if their target is hurt, all of that pain and suffering will return one day to the seeker of revenge and they will be responsible for a repayment. So nothing is truly gained, only a greater loss.