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You must have been writing your post as I was writing mine.
Most Linux distros store fonts in /usr/share/fonts and its subdirectories.
To find them, you could try as root "locate *.ttf"; this would search for truetype fonts.
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Just delete the *.ttf files from /usr/share/fonts (or from /usr/share/fonts/ttf or from /usr/share/fonts/truetype or whatever your distro calls it).
If you want to be careful, move them somewhere else where you can delete them later.
Then run
fc-cache.