Please find the below logic where it works on the condition.
If we simply call taskkill /im applicationname.exe, it will kill only if this process is running. If this process is not running, it will throw an error.
So as to check before takskill is called, a check can be done to make sure execute taskkill will be executed only if the process is running, so that it won't throw error.
tasklist /fi "imagename eq applicationname.exe" |find ":" > nul
if errorlevel 1 taskkill /f /im "applicationname.exe"