[throwaway2016a]

Netsuite comes to mind. Enterprise software. Charges hundreds of thousands of dollars a year. It tries to be everything to everyone which makes it really slow. And the menu has 500 options so it's hard to navigate.

For what it's worth, it has made me say "Wow, that is really cool and useful!" more than a few times but also very often "WTF! Why does this take so long! This is a common operation!" and "Why is this so unnecessarily complex!"

The API is SOAP and routinely takes 5+ seconds to do a common operation like "Create order" - and ad hoc searches can take minutes.

Business people like it because it gets them every critical piece of business operations data they need at their finger tips but also hate it because of the hundreds of thousands they ultimately pay consultants to deal with the complexity.

Runner up: Jira

A lot of people say Wordpress but I think a lot of the Wordpress UI is good design. Which is part of why it's popular. It is just really slow (unless you spend a LOT of time optimizing). So Netsuite wins for being both slow AND poorly designed.

Edit: That said I can't say that I wouldn't recommend Netsuite. If you are a multi-national corporation (or even a large domestic one) and sell or manufacture a physical product, and have the time and money to pay the licensing fees and the consultants it does everything you could possibly want and more. If someone asked me for a recommendation I'd say: "It's great but don't expect it to be perfect day one. It will take a year with possibly multiple full time consultants to get everything where you want it to be."