Please read up on his life. Mainlander is the most extreme/radical Philosophical Pessimist of them all. He wrote a whole book about how you should rationally kill yourself and then he killed himself shortly after.
https://en.wikipedia.org/wiki/Philipp_Mainl%C3%A4nder
https://dokumen.pub/the-philosophy-of-redemption-die-philoso...
Max Stirner and Mainlander would have been friends and are kindred spirits philosophically.
https://en.wikipedia.org/wiki/Bibliography_of_philosophical_...