If "Descent, Part I" was an entertaining but inconclusive setup episode that ended on a head-scratcher, then "Descent, Part II" is like watching a balloon slowly deflate for 44 minutes. It's not horrible — especially not in theory — but boy were we hoping for something better than this.
The episode opens with Lore explaining in lengthy fashion how he became the leader to these lost Borg and how he "helped" Data realize the "truth" about the great quest of definitive purpose ahead of them. Lore believes in the superiority of those like himself — artificial lifeforms that have no biological makeup — and he hopes to remake the Borg in that image (which has resulted in failed experimentation and brain-damaged Borg). But there's still no useful rationale for why (to say nothing of how) he wants to conquer the Federation, other than to justify the lame line that capped part one and artificially inflated the stakes.
There's something interesting in the idea that sending Hugh back to his ship caused these Borg to fall into individualized, unworkable chaos, as well as the notion that they would be willing to turn to anyone — even an egomaniac like Lore — just to quell the disorder. But all of that has already happened well before "Descent" begins, and we now get everything told to us in exposition, and I have a hard time actually picturing it. The complexity of such a task becomes a lot more prosaic when we hear Hugh (who is part of a rival Borg faction that has sided against Lore) gloss over it. Lore clearly must have done something to bring the Borg back from chaos, but the story offers no details. It just kind of happened.
As for Data, "Descent II" turns him into a puppet of his programming. There is no characterization of any interest here, because it's all a form of mind-control that Lore has instituted. Thus, Data's defection has zero character consequence. If Lore had actually been able to find a way to make a case that Data could believe in (not that I can picture one), that might have been more interesting. But instead this is just a matter of an ethical "off" switch being flipped to make Data an automaton. His thirst for the emotions Lore feeds him comes across as a half-baked analogue for drug addiction. Really, the whole would-be arc is vaporware.
Meanwhile, the idea that so many members of the crew are on the surface of the planet makes no sense at all. (More than 70 just to search for Data? Why?) This leaves a skeleton crew aboard the Enterprise, with Crusher in command, which serves no purpose but to put a character in command of the ship who normally never would be. The bridge sequences where the Enterprise engages the Borg are easily the weakest part of the episode — jam-packed with who-cares technobabble and who-cares temporary placeholder bridge characters, utterly devoid of tension or danger, and featuring a resolution that makes you shrug. (Not to mention, it employs the shield technology from "Suspicions," of all episodes. My, how Borg engagements have fallen, even from part one of this story.)
"Descent II" is a disappointment because there's clearly some underlying ideas here about actions having consequences (Hugh returning to the collective), and the susceptibility of the vulnerable being exploited by a charismatic savior who promises them greatness. Unfortunately, it's all half-formed and compromised, and executed with an almost stunning lack of urgency when you consider this is the kickoff episode to the final season of a sci-fi television giant. The most interesting character nugget comes at the end, when Data retrieves the emotion chip from his deactivated brother, hinting that one day he might install it. Too bad we now all know how that worked out.