No nagware but, at least on the machines of my colleagues, an even worse enemy: Microsoft Defender with all the checkboxes ticked. Grinds the machine to an absolute halt for any development work - sometimes the responsible security department has mercy and gives exceptions for certain folders/processes, sometimes not.
My work machine is grossly slow due to all the various security software.
Loading Teams can take minutes. I'm often late to meetings waiting for the damn thing to load.
Feels like early 90s computing and that Moore's Law was an excuse for bad coding practices and pushing newer hardware so that "shit you don't care about but is 'part of the system'" can do more monitoring and have more control of 'your' computer.