[The Great Saiyaman]

The first and second seasons were the strongest ones no doubt. And it was only sporadically that the third and fourth seasons managed to recapture that magic.

I loved those episodes which took place during the invasion, the creation of Bebop and Rocksteady and in the fourth season Leonardo working with Karai in a clandestine way, Heck there's something to be said about the "Undead Shredder arc" of the fifth season, that was the series at its best.