The most of them? What fighters were legitimately capable of stopping iron chinned fighters? Denting the undentable. Edwin Rosario seemed extremely capable of this. He stopped the ultra hard headed Livingstone Bramble like no one did before or after. He also blew out Edwin Viruet, who went 25 rounds with an enraged, prime Roberto Duran and was never off his feet. Edwin's brother had an even better chin, strangly.
Olivares might take the cake here. At the very end of his career stopping the iron chinned Jose Luis Ramirez in two. Also at the end of his career, Chacon in two.
The only fighter I can think of that stopped as many iron chinned fighters at heavyweight might be Ali, though he managed it utilizing completely different methods then Louis.
Lets see if Vitali Klitschko even makes it into the ring vs peter. we all know he has a history of being a pancy on cancelling fights.
Journeyman to fringe contender level certainly, but not easy men to stop. Foreman stopped Chuvalo, Frazier (twice), Peralta and Qawi. Pretty impressive, considering the quality of the opposition.