If you need to remove an older version of Alfred from your Mac, quit the application by clicking the hat in your menu bar and choosing "Quit". You can then simply drag the old version of Alfred from your Applications folder to Trash.
When uninstalling, we don't recommend using app cleaners, as app cleaners can be overzealous and may remove files essential to your current version of Alfred.
If you've used an app cleaner, check your Trash immediately and drag out any files relating to Alfred to avoid them being deleted permanently. You can then contact us and we'll help you reset Alfred.
Alternatively, revert to your Time Machine backup prior to using the app cleaner.