I have a neighbor who is a bear guide. He was baiting for clients during season and walked in on a very aggressive bear. The bear must have thought he came to steal his food. All he had was a .357 magnum Ruger Security Six. He said he pulled that and as the boar walked towards him gave him all six rounds. At point blank range it dropped the bear dead as snot. And he said it was impressive the damage it did to the bear.
The next year he went out, traded off his .357 and bought a 454 Casull Raging Bull Taurus Revolver. He said while the power of the revolver is most impressive, he flinches because of the recoil... So sometimes, bigger is not always better.
You want a real stopper, get a Desert Eagle .50 AE . I shot one of them once. And granted I have shot some powerful hanguns, but that one is really powerful. Almost too much for my book as you really better have a grip on that thing.