pretty simple - Frank here is an outlaw that likes to fight, and if he is more notorious than the target of his ire, the fight is going to happen.
in case you do not have a readily available way to make Mr. Bryant wanted, he can choose to make the very act of entering play a crime. So that he can get down to business.
unfortunately for some more murderous outlaw players, starting Frank Bryant does not come with that same initial bounty, so he is going to have to find some trouble to get into before his ability really turns on.