Skype for Business - I really hate this shit. Random disconnects, errors, no offline message support, idiotic message history in Outlook, random errors "Text is too long" etc.
You forgot mangling urls by inserting underscores in the url, not being able to copy and paste part of a message cleanly, stuttering audio or video when your internet connection is perfect, and screen sharing that doesn’t start or drops whenever it feels like. Oh and abysmal workflow around picking the right audio device.