The last few episodes of season one, to the end of season 3 was PEAK Steven Universe. The writing from The Return all the way to Bubbled was probably the greatest the show has ever been. And with the quality of the show, I feel that is really saying something. The vibrant colors, funny moments, great writing, and of course the peridot redemption arc. On the flip side, I feel like future is probably the lowest general point (not counting individual episodes), in Steven Universe. But again, given the quality of the show, to me that just makes it fine.
