I know the American SotN manual says each generation of Belmonts is stronger than the one that came before it. It's a bit of a simplistic way to look at things, but that's how it works apperently.
So possible candidates are Julius or if the description from Otomedius Excellent is true, his daughter (or sister, it's left ambigious on purpose), Kokoro. :P
There was only 1 Belmont that had the ability to literally rip pieces off the castle when he performed Grand Cross./thread
DEBATE OVER
Also, isn't Richter the only Belmont to use the Vampire Killer at maximum capacity? Every time he has been shown wielding it, it has never been anything but the chain whip.
But yeah, in AoS Julius uses his Grand cross on Soma and just rips apart the underside of Castlevania. However he seemed far weaker in DoS.
And this was with him HOLDING BACK against Soma, in his FIFTIES I must remind us all. Grand Cross'ing in his prime must have looked like an atomic bomb going off. Yeah that's it; he Grand Crossed SO hard he launcged the castle into an eclipse!!
Julius, because he was taught by Johnathan whom defeated whip's memory which was a Prime RichterThat and his Grand Cross can destroy a Castle