True, forgiveness of sin is for the guilt of sin with eternal consequences, and satisfaction of penance and indulgences is for the temporal punishments, but we suffer with the other current effects of our actions, and these are most like the concept of karma.
True for some karma, based upon the Vedic types of karma:
- Prarabdha - The consequences of actions you performed in previous lifetimes, destined to play out in this life.
- Kriyamana - The karma you’ve generated since taking birth in your present body.
- Adhyatmika - The karma you create as an individual.
- Adhibhautika - The karma created by groups of people (e.g., your family, community, nation).
- Adhidaivika - The cyclic destiny of the Earth itself and its natural forces (e.g., volcanoes, tornadoes, earthquakes).
Some karma can be altered per this theory. As a practice, in India, there are various remedies taken to modify karma from past life actions, so there is the concept of changing past bad karma, especially prayer, and sacrifices.
If one does not accept reincarnation but accepts the concept of karma, then that would leave just that remaining kind of present karma that could be altered.