You need to be able to access the Menu / Settings button and set back the GUI size from the left side options again, the question being : can you actually move your plugin window to access the "settings" ?
But if you really can't and want to avoid a clean uninstall/re-install process, you can delete the Kick 2.settings file that should be located under the following path on a MAC ( you should find the equivalent under Windows too ). Once this settings file deleted, upon reopening Kick 2 in a new instance of you DAW it should revert to it's default settings by creating a new settings file.
That should do the trick
MacOSHDD/Users/YourUserName/Library/Application Support/Sonic Academy/Kick 2/Kick 2.settings
UPDATE : If you're on a PC, the WIN path should be : C:\Users\YourUserName\AppData\Roaming\Sonic Academy\Kick 2\Kick 2.settings Note that the AppData folder is hidden by default on Windows, you'll have to make hidden folders visible in order to access it, just Google it to find how if not familiar.