Can one rid oneself of Karma or must they let it takes its course; is there any way around the effect of Karma once you have sinned or committed an act of evil?
There is no escaping the result of one’s actions but, by performing good actions, it lessens the effect of one’s bad actions. Imagine that the result of one’s bad actions is like a handful of salt and that one’s good actions are like water. If you put the handful of salt into a glass of water, the water will taste salty. However, if you throw the handful of salt into a freshwater lake, it would be difficult to detect the salt taste. The same amount of salt has a different effect in each case. You also mention ‘sin’. There is no such thing as ‘sin’ in Buddhism. There is only the action of an unskilled mind – a mind ignorant of the effect of one’s actions on one’s self or on others. A skilled mind exercises mindfulness or awareness and thus avoids unskillful actions.