Plenty of left hook artists in the middleweight division those days, Lausse, Fernandez, Hurricane Carter. Lausse's left was the best of the lot I'd say, although the rest matched him in power.
Another great forgotten middleweight left hook...Lindell Holmes. Didn't quite carry his power up to 168 though.
I have McClellan as the hardest puncher on the list provided. Some guys that should be in the conversation for sheer power at 160 are Maseleno Masoe and David Lemuex. Both guys had/have brutal lefts hooks that could close the show on anyone. To bad they both had deficiencies elsewhere in their game.
I said "almost" everyone forgot about him, and honestly, Sosa is in the stage of being forgotten IMO. Forgotten does not literally mean that everyone forgot about him, if only a few amount of people know about him can also be considered forgotten. Let's say that there's 1 000 000 people in this world and only 100 people remembered about you, that can also be considered "forgotten". One more thing, why does no people mention about him does not mean his not forgotten? If no one talks about you, you're probably forgotten. It's like saying that you left a village and all the people from the village didn't even talk about you or even spoke your name and your not forgotten? That doesn't make any sense.. (at least for me) I apologize if I was being a hipster and it was irritating you. I'm sorry.