You might want to check out this earlier answer of mine for Stasi prosecutions.

I know a lot of Stasi officers were prosecuted, but not much more.

This is not true. According to Mike Dennis's research, around 98% of the inquiries into Stasi agents were abandoned and only twelve officers had received a sentence as of 2014. There were some high-profile prosecutions of Stasi leaders like Markus Wolf but they fell apart. The reunified government tried to prosecute some of the SED leadership for violating German law. Most of the time this involved manslaughter charges for being the ultimate authorities responsible for shooting border violators. But these trials were often mired in procedural issues and dragged on long past the public's interest (this was too a distant mirror of the various postwar Nuremberg tribunals which were nowhere near as successful as popular memory holds). The prosecution was that there were few specific laws that could apply to the SED's actions. SED union leader Harry Tisch was an exception in that his embezzlement of funds presented a clear crime. There was a conviction of Wolf for treason in a local court, but the German supreme court overturned this conviction because Wolf was acting on behalf of what he construed as a sovereign state. Yet it was far harder to pin legal responsibility for the shooting orders on the SED elite and a number of those brought to legal proceedings contended that the Soviets were the origin point of the order. The aged leadership of the SED also posed a problem as many of these men were of advanced age as the trials dragged on and their health issues contributed to the German government's gradual abandonment of prosecutions. There was slightly greater success in prosecuting lower-level border guards. All of these trials though attracted a good deal of negative media coverage especially as a number of defendants like Egon Krenz would claim that the reunified government was less interested in the law than on putting the GDR on trial. Given all of this public kerfuffle, the few sentences for GDR defendants received were incredibly mild and often overturned or commuted.