"stupid powerful" if you are looking for more power there are many cartridges more "powerfull" than the 45-70, even the 450 Marlin ( which looks like the 45-70, but a fraction longer, so it can't be chambered in older weaker guns )in factory loadings is slightly "hotter" than the 45-70... there are a pleathera of belted magnums that are more "powerful" than the 45-70... if you are looking for a bigger bore... you almost need to go to 50... there are several .475's but they are more obscure ( reads more expensive / harder to get ammo for etc. ) I have a custom Marlin lever action in 50 A.E. that I load a heavy cast bullet for, the conversion turned my sweet little 44 mag lever into a litteral beast that required glassing up the foreend to keep it from rattling apart under recoil... I also like the old 50-70 Gov. but that is not as hot a cartridge as the 45-70 can be loaded to...
the 500 S&W in a rifle would be a bigger bore & a monster to shoot... there is also a 50 Alaskan, that's generally chambered in lever actions, & that is more powerful than the 45-70
I've been expirementing with both a custom 53 caliber rifle, & the 577 Snider, but these are both low pressure rounds, so while the bores are much bigger, they are no match for even the 50 A.E as far as power, & the 500 S&W probably ( I've never looked up the energy ) but is likely twice the energy of the 50 A.E.