Our destiny results from karma indulged by us alone. No one else is responsible for our destiny. Karma includes mass karma enacted by the entire family, close relatives and friends.
As the residual balance of karma accordingly shapes our destiny! But the control of destiny never lay in karma indulged by us in present life alone. A portion of karma from previous lives manifested by us can fructify any given moment of life.
Is this residual balance of karma from previous manifestations is negative, one all of a sudden undergoes sufferings for no fault of one in present life. If the residual balance of karma from previous manifestations is positive then all of a sudden one experiences extreme happiness, if luckier one can win a big lottery.
One can never reverse workings of karma of previous lives but we can gradually undo, neutralize the same by indulging in good karma, positive karma all throughout in present life.
Karma is only a hidden underlying principle of life. If we suffered in present life, it resulted from our indulgence in karma in past or previous manifestations. So was the case with experiencing happiness. As a human being, the highest manifest stage in cosmic life cycle it becomes our duty to indulge in good karma, positive karma most of time as did by Mahavira, Gautama Buddha even Jesus Christ and Prophet Mohammed.
All the above man gods were highly realized souls, prime reason why they indulged in spirituality for the benefit of entire mankind.
Karma of its own can do nothing. It is karma enacted by human beings that finally shaped our destiny. Human beings who blamed God Almighty for their woes were a mistaken lot.
Can Karma change our destiny is akin to saying can architecture design my house! It is not the principle but the architect who designs the house. As karma is enacted by human beings, if we suffered, it was due to our own folly our actions.