Which blat Gemara (Bavli, Vilna edition) has the largest quantity of Talmudic text or the most complex and difficult to understand concepts?
If you're just looking for long talmudic text, there are others in Brakhot with little commentary: See Brakhot 56b, 58.
Difficult sugyas with little Talmudic text and plentiful Tosafot/Rashi are qualitatively longer (and scarier!) than the more aggadic, pshat texts. There are a few in Niddah that make you hold your breath when you first turn the page onto them: See Niddah 10a, 18, 67a.
The longest battle, imho, are the four days studying masekhet kinim.