Anything a user tries to do to ask for help is correct behavior that you need to support. It is a crime to tell the user “you asked for help incorrectly”.

I suggest supporting at least all of the following: -h, -help, --help, -?, /h, /?, help, <no flag> (if possible). Other flags don’t have to follow these rules, but I think help can be an exception.

And maybe you should print the help any time the user enters a bad command.