How strong is karma?

[anagogy]

If we do bad to other people, it will probably come back to us in another life. Or we will choose to experience bad things in our next life.

What if we never really hurt others?

Then you incurred no imbalance that would require rebalance. If experience imbalanced your spiritual energy, then experience of a reciprocal nature would re-center that energy.

Would we still experience abuse in another life?

Only the abuse that was drawn by your imbalanced choice of thought. Thoughts of separation attract separation. Thoughts of unity attract more unity.

Is there a time where we would choose to experience abuse on purpose? Does a good life create good karma?

Souls volunteer for different experiences for a multitude of reasons. Sometimes a soul will volunteer for such a role to teach the abusing soul a valuable soul lesson. Sometimes terrible experiences galvanize people to some kind of profound societal change. It is not always the case that if you are experiencing abuse it is the result of karma. It always is created in the moment. Even karma works on your thought. Desire directs thought. If your spiritual complex is out of balance, desires will form in you that will attract the experiences necessary to realign your consciousness.

There is also the automatic and mostly unconscious asking and answering of Source. When subjectively negative things happen to you, you unconsciously, and automatically ask for improved experiences. The preferences radiate from you vibrationally whether you're aware of them or not. Your preferences are part of your soul pattern. There is no confusion to Source about what you want and who you are. These improved experiences are queued up into your future, when you achieve proper alignment with them (following your heart/bliss). You might call those queued up desires positive karma.

In the same way, when you are cruel to others, you unconsciously and automatically ask to be nicer, because the Source part of you never has a negative opinion about anyone, so in that moment, when your thoughts and actions separated you from the Source inside of you, the preference to be nicer is automatically radiated. Those experiences which will teach you to be nicer are queued up into your future catalyst. Some people might call this negative karma. But hopefully you can take a more enlightened view and see that no karma is actually bad. It is simply imbalance seeking balance. Separation calls out for unity. Falsity calls out for truth eventually. That Which is Not eventually calls out for That Which Is.

The water of consciousness always seeks its level.

If we make mistakes in a life can we by forgiveness of ourselves make up for that karma?

Yes.

Karma is just the oneness of the universe peaking out from behind the curtain saying, "You are everyone and everything, and because of this unalterable fact you cannot hurt others without hurting yourself. Also, you cannot help others without helping yourself." It is imbalance seeking balance. It is unconsciousness seeking consciousness. If you can become fully conscious of the effect you had on another, then the karmic effect is mitigated by you making yourself fully conscious of the suffering you caused. But "fully" aware is a tall order. The attempts to understand your actions effect serves to mitigate the accumulated karma, though. That is to say, it helps to restore balance even if you don't succeed in completely forgiving yourself for the negative act (as true forgiveness requires true understanding). Your attempts to understand soften the karma, and in exemplary and extremely efficient cases of the use of mental catalyst, it will completely absolve the karma.

Will we truly in our life review experience all the pain we caused another? I heard this can be overpowering.

Yes. It's not the same though, because you are seeing it from a broader perspective. It would be more traumatic for the experiencing soul because they are experiencing that pain without access to the broader perspective. So to fully understand it, you have to experience it some form. It's not always necessary unless it was a severely separating/imbalancing action.

Also, except in the case of severe imbalances, karma will resolve itself in this life. You tend to gradually "sweat" out imbalances over the course of your lifetime.

I've been mostly kind to people. I've been mean a few times to animals. I'm not the nicest person, but I do have a lot of love.

I don't think you have much to be concerned about, Gemini.