Batman encountered the eccentric Billionaire Baxter Baines only once, in a two-part 1978 story by David V.Reed and John Calnan. Baines is dedicated to exposing The Batmans secret identity and has put a lot of time (as well as his own considerable resources) into it. He publicly reveals clues as to The Batmans identity and actually comes painfully close to figuring it out. To this end, Baines even develops a costume of his own and hatches a brilliant scheme to bombard the Dark Knight Detective with special light rays that can only be seen through a lens of his own design. He then plans to use the lens to track Batman in the day (by this time, he has already deduced that Batman is a wealthy member of Gothams social elite). Of course, Batman gets around this by staying in the next day and then uses the same technology to catch a cult of murderers from the Caribbean. Oh, Batman, there's just no stopping that dude. Eventually, The Dark Knight outs Baxter Baines himself as being Batman and, in the resulting media (and criminal community) fallout, the enigmatic Billionaire leaves Gotham for Capri. As a combatant, Baines proved himself to be nearly as effective as The Batman and he was also shown to be fluent in several languages, a gifted athlete and a genius inventor. In his single appearance, Baines was an intriguing foe for The Batman, he was sort of like a mischievous alternate version of Bruce Wayne (if he had chosen to become The Riddler instead). It is doubtful that this rogue will ever be seen again, but personally, I hope he does return at some point. There's a lot of story potential there.