The Ghost-type Pokémon Gengar used to be in Xeno Fighters R back in May 2009 (it wasn't even called Xeno Fighters R back then).
Let's say Gengar is to 2009's Xeno Fighters as Ultima-X is to Xeno Fighters EX. We sent Gengar back to his Pokéball when other people saw how overly powerful he was.
Gengar used Gastly and Haunter as Slaves. He has a wide AND rapid-firing main shot. His loadout:
Laser: Dark Pulse (basically a full screen nuke fired off every second or so)
Missile: Shadow Ball (actually a reasonable weapon, but overshadowed, pun intended, by his main shot and Dark Pulse)
Bomb: Hyper Beam (a huge laser that can kill bosses with one hit, much more powerful than Vic Viper's bomb)