A significant amount of people are familiar with the general concept of karma, of which, whether one believes in karma or not, karma exists, nevertheless. Basically, karma is the spiritual law, that you surely do reap what you do sow, so that those that are so delighted to get over on somebody today, or to lie, or to cheat, or any of the negative attributes that are not harmonious with brotherly love, fairness, and justice, will, in general, create specific karma for that individual, that must be met in a future life, if it is not resolved within the current life. This does not mean, that the exact harm that a given person does must be overcome in the exact same circumstances, but it does mean, that the imbalances in a given person's life must be fairly met, so that, if you have a history of taking from others, you must, in one way or another, in one form or another, give back.
Of course, human nature, is often looking for workarounds from having to suffer the penalty of balancing out bad karma, thinking perhaps, that prayer, general niceness, and so on and so forth, are good enough to overcome such, and perhaps for some people, this does indeed work, but within a given person's heart, what is necessary to actually be accomplished is intuitively known. In addition, for those that have gone down the wrong path for long periods of their life, sensing that they are near the end of their physical presence of earth and then wondering what they can sincerely do to make up for the wrong that they have done as their time is now so very short, the basic answer, is that every step that you have taken down the wrong path, must be met with a step taken down the right path, and though you may not make the journey back to the straight and narrow road, at least the progress has been commenced with the steps taken in the right direction.
As in any rule, karma, included, there are exceptions to such a rule, of which, great souls, such as the Christ, other prophets, heralded or not, good people of all stripes, can, if they so desire, take on the karma of other people as a tribute made to God, for the benefit of those have committing such bad karmic acts. This is no light step taken from these dedicated souls, for the karma they take upon them, including mass karma, can create real physical illness, financial destruction, shunning, ignominy, injustice, and all sorts of havoc that another should have suffered, but these few will take upon themselves, even unto death itself, including crucifixion.
There are no free rides in God's kingdom, and simple basic little cursory prayers are not going to correct wrong acts, though prayers and right thinking may indeed turn things around, but the bad karmic mess previously created must be cleansed in its entirety, without exception. This signifies that those that are caught up in this world will continue to suffer the slings and arrows of outrageous fortune, until such a time as they correct themselves in a manner that reflects that they recognize that acts of disharmony to God's law are injurious to the individual, demonstrated by the karma incurred.
We are fortunate, that in every era, master souls incarnate amongst us, to guide us, to teach us, to have us to learn by example, of which no greater illustration, is this, that: "Greater love hath no man than this, that a man lay down his life for his friends" (John 15: 13), which is the epitome of he who has taken on mass karma (sin) for us.