Least favorite enterprise software (so far) is Oracle JD Edwards (but more specifically the integration between systems).
Unfortunately a board member was friends with an employee who recommended JDE. It required full time maintenance and a few years later that employee left and the company wrote off over a million dollars to go back to the old (but slightly updated) system.
Following that, a board member (the same one I think) agreed to have another friend's security business install CCTV across the branches. The project was not scoped and no thought had gone into it, making a real mess for the IT department to sort out (provided hardware was under spec'd, existing networking equipment needed replacing, etc)

Who do these upper management people think they are that they can make decisions based on little fact or research and expect the people beneath them to just magically make work.
The huge salaries of those people is not justified. We're the real workers who actually get stuff done so the pay and appreciation should be spread accordingy.

Rant over.