Not only that, Batman isn't even the strongest powerless rich superhero. Ironman dunks Batman. In his own niche superhero role consisting of no more than like 4 people, Batman isn't on top.
Captain America has gone toe-to-toe with Iron Man on more than one occasion, and as I mentioned already, both Batman and Captain America are described as being at peak physical strength of what a human can be.
Outside of that, Captain America has his pride, and instincts. Batman has his genius, peak martial arts prowess, and tons of gadgets. In the event that Batman and Iron Man fought each other no-holds barred, expect that Batman has a way to lock that suit down before he even gets to use it.
I just want Card Sagas Wars. Seriously, I'd do anything, just give me Card Sagas Wars. Please. PSN:ChocoboDreams
if you mean actual power, then the best way to know would be to have all champs fight each other at Level 18 with no items(viktor has his default core and rengar has the bonetooth necklace with no trophies), and honestly, I don't think there's actually the weakest champion, all of them can pull their own weight
if you mean lore-wise, then idk, I'm not familiar with all the lore, but I'd say that the ones from the Void, the imprisioned ones and the Shadow Isles are probably the strongest ones