I think it would be good if the Readme warned people about false positives.

Even if SUCCESS: Sent termination signal to the process "abc.exe" with PID 123 is returned, there is no guarantee that the process will actually be terminated (see example below) - it's just sending the signal, not more, not less.

λ tasklist /fi "imageName eq boinc.exe"                                     
                                                                            
Image Name                     PID Session Name        Session#    Mem Usage
========================= ======== ================ =========== ============
boinc.exe                    12312 Console                    1     14,108 K
                                                                            
λ taskkill /im "boinc.exe"                                                  
SUCCESS: Sent termination signal to the process "boinc.exe" with PID 12312. 
                                                                            
λ tasklist /fi "imageName eq boinc.exe"                                     
                                                                            
Image Name                     PID Session Name        Session#    Mem Usage
========================= ======== ================ =========== ============
boinc.exe                    12312 Console                    1     16,616 K
                                                                            
λ taskkill /im "boinc.exe" /f                                               
SUCCESS: The process "boinc.exe" with PID 12312 has been terminated.        
                                                                            
λ tasklist /fi "imageName eq boinc.exe"                                     
INFO: No tasks are running which match the specified criteria.              

Just to be clear: the warning should apply to the force option as well: for example, if you are trying to kill a task that depends on a service, you will have to kill the service first.

There are also the usual suspects, of course: insufficient permissions, unkillable system processes, faulty driver processes, etc. All in all, you should probably always check whether the process you tried to kill was actually killed.

PS: Just in case anyone wants to parse the taskkill output to report info, success, errors, etc. in a more user friendly way: please note that these messages are i18n'ed (for example, in English: SUCCESS: ..., in German: ERFOLGREICH: ...).

PPS: It might be worth investigating what the pros and cons of using taskkill compared to wmic or Stop-Process are. Perhaps there's a better way to kill stuff on Windows ... I only know for a fact that shutdown /t 0 /f /r is very reliable when it comes to killing processes. Unfortunately, however, it has terrible performance. :/