I’m one of the many people who have had problems with the latest version (7.0.1473) and had to uninstall it.
The process was made more difficult than it needed to be by virtue of the uninstaller being larger than the allowed 640*480 safe mode screen resolution, a fairly glaring oversight considering that uninstalling in safe mode is one of the most common scenarios.
Uninstalling avast should be done in normal mode if possible, disabling avast’s self Defense in Settings/Troubleshooting can help with the removal also if you are not the system Administrator and if this process doesn’t work then use the removal tool in safemode.