1. Small, fixable failures: software crashed in production every night at 4AM.

2. Utter failures: long ago tried to do something like https://capnproto.org/, wasn't up to it.

3. Worked on many projects that were replaced or cancelled a year later; the largest was an airline reservation system.

4. Started a startup, it failed due to lack of attention to what users wanted.

You can hear full version of these stories and how to avoid other failures of mine at https://softwareclown.com

I worked for an MLM company that was flying high when I started ($400M+ annual sales) then tanked and closed. Team of about 30 devs and sys admins built a complete e commerce system, duplicated outlook as a web app, and a lot of other stuff. All that software is gone. Best team I've ever been on. Projects didn't fail but the company did.