Windows? There is not an day me amd my colleagues have to fight with windows because of an problem in there, built in drivers that stop working or apis that have an probability to work of 30%.
Old versions of embedded windows and the ancient versions of android that zebra devices run. Anyone who has worked in a factory or warehouse or shipping hub etc can attest to that.
Windows CE (aka wince), it's windows, with all of windows' bugs, but intended for embedded applications, making debugging even worse.
Microsoft Office (word especially) for macos. I’m required to use at the moment, but oh boy for decades old, mature software it’s frustrating buggy.
Some proprietary trading or matching software built on MS Office 98 tech stack.