Yeah, many people have pointed out that Sylas shouldn't have that physique considering the conditions he was imprisoned with.
But what can you do, Riot is on a mission to keep adding "sexy males" to the game, hence why we get champions like Sylas, Aphelios, Sett, and so on in the last time.
But I kinda see a point why they wanted him to be a great threat. Sylas is basically the only villain coming from Demacia to this point.
Besides him, in the Demacian champion line up there is not a single criminal or something like this... they are all serving the Demacian crown to some extend and are loyal.
This is something that I also criticized about Piltover in the past. Until now, we don't have any real criminal/villain coming from Piltover, up to the point that the only antagonists for their stories need to get pulled from the Zaunite champions, like Jinx, Urgot, or Viktor (not actually a villain, but demonized from Jayce' point of view to give him an antagonist).
We need variety for the different regions, so I hope we will soon get an evil Piltovan to mix things up a little. You are right that this needs to be handled differently, tho. They shouldn't be just a plot device with seemingly no weaknesses.
