To uninstall Tera Term, run "Programs and Features" in Control Panel, or run unins000.exe in the Tera Term directory.

If the uninstaller does not work, you can uninstall Tera Term Pro manually. Delete all Tera Term files in the Tera Term directory and remove the "Tera Special" font from "Fonts" in Control Panel.
If a user uses the Tera Term Menu, delete the HKEY_CURRENT_USER\Software\ShinpeiTools\TTermMenu registry.