Hugh reappears in the episode Descent Part II where we learn that Hugh did indeed make the Borg into individuals... but that the result was chaotic and left them open to being manipulated by Lore (all quotes from this transcript, emphasis mine)
TROI: Are you saying that you caused them to become individuals?
LORE: No, you did that. You and your friends. All I did was clean up the mess you made when that Borg you befriended returned to his ship.
DATA: Hugh interfaced with the others and transferred his sense of individuality to them. It nearly destroyed them.
HUGH: Why are you here, Commander Riker? Hasn't the crew of the Enterprise caused enough damage already?
WORF: So you blame us for what has happened to the Borg?
HUGH: You gave me a sense of individuality, changed me, then sent me back to the Collective. You must have known that change would be passed on to others.
RIKER: We considered it. We knew it was a possibility.
HUGH: Then you made it possible for Lore to dominate us.
WORF: I cannot accept that. Lore is only one. The Borg could have stopped him.
HUGH: You don't know the condition we were in when he found us. Before my experience on the Enterprise, the Borg were a single-minded Collective. The voices in our heads were smooth and flowing. But after I returned, those voices began to change. They became uneven, discordant. For the first time, individual Borg had differing ideas about how to proceed. We couldn't function. Some Borg fought each other. Others simply shut themselves down. Many starved to death.
RIKER: And then Lore came along.
HUGH: You probably can't imagine what it is like to be so lost and frightened that you will listen to any voice which promises change.
WORF: Even if that voice insists on controlling you.
HUGH: That's what we wanted. Someone to show us the way out of confusion. Lore promised clarity and purpose. In the beginning, he seemed like a saviour. The promise of becoming a superior race, of becoming fully artificial was compelling. We gladly did everything he asked of us. But after a while, it became clear that Lore had no idea how to keep his promise. That's when he began talking about the need for us to make sacrifices. Before we realised it, this was the result.
RIKER: What happened to them?
HUGH: Lore began to experiment, trying to re-make us in his image. This is the result of my encounter with the Enterprise, Commander. So you can see I don't particularly welcome your presence here.
RIKER: I'm sorry you feel that way. We just came to get our people. We won't cause you any more trouble.
This exchange is at the end of the episode
HUGH: Perhaps my encounter with the Enterprise affected me more than I realised.
PICARD: What will you do now?
HUGH: I don't know. We can't go back to the Borg Collective, and we no longer have a leader here.
PICARD: I'm not sure that's true.
HUGH: Perhaps in time, we will learn to function as individuals and work together as a group.
PICARD: Good luck, Hugh.
Star Trek: Picard showed what happened to him afterward
Hugh eventually becomes "reclaimed", in much the same way Seven-of-Nine was, where most of his implants are removed and he re-grows hair. Hugh directs the Romulan Borg Reclamation project, where assimilated people from a "de-collectivized" cube are having their implants removed and some semblance of their former selves restored.