Well, it’s kind of a given that a big club and top class coaching team will develop players further, and you also have to assume some time for players from abroad to adjust to the Premier League etc but, off the top of my head, Ederson, Walker, Dias, Gundogan, B.Silva, Sterling, Mahrez, De Bruyne, Cancelo. Then some that were young but with the potential to become World Class, like Stones, Ferran Torres, Jesus, Rodri - these are at various levels of success.
I’m using a looser definition of ‘world class’ - eg would walk into most teams in the world, let’s not get hung up on some childish FIFA type definition of world class like “best in the world in their position” or “gets into a World XI” please.