"They brought the 458 Win Mag out in 1954,"

Maybe that makes four mistakes since '37!!

If I recall correctly the .458 Winnie was developed for the market in 1956. By several books and Model 70 serial numbers I have seen '56 is correct, but like anyone else I could be wrong. I still remember Jack O'Connor's O. L. article on its introduction and the picture of the .458 he had Al Biesen build him on a Model 70 action that as he said, "he conned a pal out of." Just a side light.

Anyway, I agree 100% on what you say about the .458 Lott and it's loading. Funny thing, there was no reason for the Lott, we already had the 450 Watts, but I guess Lott needed his name on a wildcat of his own to promote more writing sales. For sure he wouldn't want to talk about how poorly the buff was hit with the Winnie.

There is more than one way to consider big. Bore diameter, case capacity, case length or whatever.

Assuming bore diameter, then .600 Nitro. Hardest kicking is hard to say. Too many years have gone by on some of them, but I recall a H&H Deluxe .577 Nitro made in '62 at a fraction over 10# being a real beast with its 24" barrels.