Some of them can be deleted via Windows 'add or remove programs'. Otherwise:
Delete *.addin files and *.dll files in these folders:
Some user specific addins are located within the %UserProfile%\AppData\Roaming\Autodesk\Revit\Addins folder.
The alternative location for addins for all users is C:\ProgramData\Autodesk\Revit\Addins\
yes that is it. You have to find by starting, not at "add or remove programs, but in Control Panel\programs\programs and features. Had a nasty run-in with "BIM Helper Tools" trial version.
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