I'd bet my house on both Mosley and DLH stopping Tszyu. Especially Mosley. Tszyu, plain and simple, did not have the heart and the chin that Mosley and Oscar had. I don't care much what he did to Forrest in the amateurs. Forrest clearly beat up Philips as a pro, yet Philips still dismantled Tszyu.
Fair enough, like I said before regarding Phillips, you have to take in account his out of ring issues when evaluating him. When sober, he was a very good ( not elite) fighter. When coked out, he was just a guy. Tszyu was not prepared for Phillips and that is on him. I wouldn't necessarily favor him over Shane or Oscar but that doesn't make Tszyu any less of a great fighter. Just not as good as some other hall of famers. I do think he matches up well with Mosley but I wouldn't favor him.
I vote Tszyu. But I am a Hamed fan. He actually got me into the sport back in the mid 90s. I 'm not saying he's amazing, but I think he was better than some people have him today. He was unique and powerful and had some good wins while he ran through the featherweight division in the late 90s (e.g. Johnson, Medina). I do think he would always have struggled against a highly skilled boxer like MAB... but I think he was better in those early days - a harder worker, more focussed in training, not overly reliant on power). By the end he had become a bit of a caricature of himself and was an accident waiting to happen IMO.
There`s no way Barrera would have toyed with a fighter on the level of Tzyu the way he toyed with Naz.
Hamed was past his prime and Tszyu never fought anyone as good as a prime Barrera. Not that I'm saying Tszyu would lose a wide decision to someone like Barrera but some context is needed.
Watch the documentary in the lead up to the fight its on YouTube. I'm not saying Hamed ever beats Barrera but he did take the fight too lightly.
Pretty much all fighters, even great ones, lose. Especially when they face super tough competition from early on. Kostya faced Juan LaPorte, albeit and older Juan Laporte, in his fourth fight. Then faced Sammy Fuentes, Livingstone Bramble and a tough as nails spoiler in Hector Lopez, all in his first 11 fights! You have that kind of schedule and you usually rack up a loss or two, even if you are great.