The Fall of Centauri Prime - I'm just going to say it right away. I hated this episode. Don't get me wrong, for what it had to do (set in motion the events seen earlier) it wasn't bad, but the overall story of Londo's fate sucks, so this story was still not good. Londo and G'Kar had great performances, especially in their last scene together before Londo becomes a puppet. But, their talent is wasted in such a crappy plot. Having a short Londo montage at the end felt like a kick in the face, and a borderline taunting of Londo's fans by JMS. This whole Londo fate plot has been bad from the beginning, from the spoilers to the very idea. Its easily the worst plot in B5, and the stupidest character stuff. The fact that Londo is my favorite character makes it even worse. JMS couldn't have written a worse plot for Londo if he tried.
I think that's the sole reason you don't like the plot. And that's why it's "bad."
It's a great story. It's a tragic story. The Londo we met in Season One would NEVER have done something like this, for the greater good. One of the reasons its great is because it IS tragic. Star Trek would never have gone there. Everyone lives happily ever after. Except for Tasha.
Londo's story is deeply moving. I'm sorry you think it's bad. But it's not. It's just not. You don't like it because you think your favorite characters have to win all the time. That's not life. That's not good fiction.