Been pondering how to try and explain how I see Harry as a player.
I don't think he was a great strategist. I think he was a great opportunist. Of course he had to make decisions like they all did, but I don't think he was a master strategist. He was fortunate there were quite a few coat tails for him to ride on, for example Paul being such a big character from the start and being so vocal. I don't think Harry was the puppet master he later tried to make out to be. Similarly, picking up that Mollie was gullible and therefore useful and cultivating that relationship was taking advantage of the situation.
I also doubt he could have played any other character apart from the cheeky chappy. He was lucky it was the one which sheep people are susceptible to. There's a lesson there for everyone!
So at the end, I'm undecided. Was he the greatest traitor? In simple terms, yes of course, because he won. But I actually think it's more that he was the luckiest, rather than the best.
Think about the various cross roads during the show... if the team had chosen to save Paul instead of Andrew from the dungeon (not implausible although it was a gamble by Paul), if Harry hadn't got the shield.
Wonder boy certainly got lucky many times!