Worth repeating: a comment by Silver Rain:
Justice isn’t ours. In fact, the very essence of forgiveness is handing our need for justice over to the Lord. Just as the Savior atoned for our sins and errors, He also atoned for the sins and errors of others. If we truly trust Him, we will find a way to allow Him to repay us whatever others owe us. Rather than expecting the Church to exact justice, which will only extend the misery this man has inflicted on your friend, taking advantage of the Atonement will free your friend from the shackles of this man’s sin. [...]
If there are Church courts where justice is being exacted, I submit the men ministering those courts do not understand their purpose. Excommunication and disfellowshipping are not exacted under the law of justice, but of mercy. If people are not keeping the covenants they made, it is mercy which requires they be released from those covenants until and unless they have repented to the point where they are prepared to make them again.
Excommunication and disfellowshipping may feel like punishment (or justice, depending on perspective) but that is not their purpose. In my understanding, courts are instructed to refrain from exacting those consequences unless the Spirit confirms it is necessary for the individual to truly repent.
As far as watching an ex-spouse be sealed in the temple when an individual cannot, I can certainly understand the pain that would cause. But that loops back to trusting Jesus Christ, Alpha and Omega, to exact the amount of justice necessary and no more or no less. Demanding He judge in a certain way means that you do no[t] truly trust His wisdom and love for the perpetrator AND FOR YOU. I have full confidence that if my ex is ever welcomed back into the family of God, it will only be once he acknowledges the damage he has done and repented for it. Who can justly ask for more than that? My ex cannot undo the pain he has caused me, nor the damage he has done to my life. But that isn’t his job, even though he was the one who committed the sin in the first place. It is the Savior’s job, and I rely on Him to “pay” me what I am owed: to make it all right again.
Fortunately for us, the Savior rarely simply pays us back. In my experience, when He pays someone’s debts for them, it comes with more interest than I would have ever thought to ask for.