The question asks about software and not specifically applications, so the worst software that I have to use are all of the web developer "tools" and frameworks

The question asks about software and not specifically applications, so the worst software that I have to use are all of the web developer "tools" and frameworks that I have to deal with. I can write far more performant applications in a fraction of the time without the bloat that is expected in web apps these days, but I would be hard-pressed to find a job where I can do that.