[Suzu]

As for the whole Tendou/ Tsukasa/ Mary Sue-thing, I'd say Tendou perfectly fits a possible Sue-definition as he is in fact a character, 99,9% flawless and so on and Kabuto overall feels a lot like a fanfiction.
As for Tsukasa, you could call him a Mary Sue, but I'd say he's even less than that. Tsukasa was not a character, he was a placeholder for whatever shit the authors felt like doing with him. There were episodes were he was an awful person (like the Blade world, with him constantly picking on Kendate and than indirectly admitting he was having fun doing so) and other episodes where he was not that bad at all (I'd say he was kinda okay in the Shinkenger episodes, for example). He never had a really consistent character, nor development because he acted different in every single episode.