Hagler was very skilled himself. He just couldn't outbox Thomas Hearns from the outside because it was Thomas Freaking Hearns. Hearns was extremely hard to outbox from the outside, outboxing Ray Leonard and Wilfred Benitez. But Hagler outboxed most of his opponents and was a versatile and pretty complete fighter.
Who did any of those fighters beat at LW? Mosley best win is what Holiday, Pacquiao only had one fight there vs Diaz, Mayweather had like 4 fights 2 vs Castillo, Hoya has more depth as he started at LW. Castillo has a who's, who's of every top LW on his resume and a W vs all of those including in a lot of opinions Mayweather himself. Head to head is proven in the stats. Castillo has the deepest LW resume in some time you should do some research. The fact that Castillo arguably has a win over the best fighter of this generation should tell you something.
He's a fraud because he LEGITMATELY beat Cotto into submission. He made Cotto go to his knees & QUIT!! so I guess he did derail his career, Cotto couldn't even beat him in the rematch despite Margarito only having one good eye for 8 rounds. That NY doc had to save Cotto from quitting again Cotto couldn't do it alone Ive known Tony Margarito since 1999 watched his hands taped many many times including Cotto 1 & have NEVER seen anything illegal he's never needed it I'm a fan & a friend of Tony Margarito & am proud of it