In what other ways does committing suicide create negative karma that holds a person back from progressing on their soul journey?

Saying "no" to life is saying "no" to the divine and saying "no" to the yearning of the soul. It is a desecration of the divine origin you represent. It is a wound to the soul in a major respect. It is an assault on the self at all levels. So, there will be a karmic consequence. The most immediate is the termination of life itself, the ending of possibilities of the physical lifetime, to create forward progress in the soul journey. It is taking a backward step and that can be compounded many times. When people reincarnate they will come back into the very same circumstance, or worse, and face the challenges all over again. If they are not up to the challenge and choose suicide, yet again, the karmic burdens will increase and any attempt to continue as physical human will be yet more difficult. This is karma in action. The idea of "What goes around comes around" is not only true, it is an understatement of the dynamics of energy. Karma grows on its own because of consequences beyond the self. When you take your own life and thereby change the lives of others for the worse, when you return you will not only have the debt and burden of the life you took, and the wound to your soul to now manage, in needing repair and restoration, and restitution of some kind, you will have all the pain you caused to others by being absent. It is not only obligations to friends and family to not darken their world through witnessing your plight, but all the good you could have done had you continued with your life, and been a part of the lives of others in your soul journey, according to the life plan you agreed to for the incarnation into the present lifetime. There were many things you had expected to do, although not aware of consciously, that will now be undone, and this will be to your detriment. You will have failed the contract, you will have failed an obligation to be there simply to assist others as well as yourself. So, it is an abrogation of duty of great significance no matter what your perspective might be in moments of torment, in the throes of depression and suffering. So, this is yet another obstacle you create for yourself, that your burdens will increase from indirect consequence of your passing. The karmic burden you inflict on yourself will be there indefinitely until it is rebalanced. It will have an impact in some way on all of your future, wherever you go, and in particular, returning to the physical existence in another incarnation. This will be a factor in determining your happiness. So, there is no escape through suicide, there is only a worsening of circumstances. This is not a punishment from God. This is you punishing yourself. That is what karma is. It is your creation being personally experienced. You create good that becomes amplified as a result of its existence in spreading outward, and you create ill as a result of your existence when you do dark deeds, and this increases as well as it spreads outward. Both the good and the bad will return again and again with the looping of time. So, the consequences are profound and will be ongoing into the future, indefinitely, and will often grow if they are neglected. These are the forces you unleash with a rash act or even a carefully considered but negative one.