Shinzon was actually a pretty good villain...
- Shinzon is a clone of Picard created 20 year before, but there's no indication why the Romulans would have considered Picard to be an important figure twenty years ago.
- Shinzon wears a ridiculous costume straight out of a Tim Burton Batman movie.
- Shinzon claims to be acting for the good of the Reman people, who he considers to be "brothers." However, every action he takes is completely self-centered and not in the interest of anyone but himself. Even the Viceroy gets angry with him about this.
- Shinzon needs Picard's blood to survive, so instead of simply telling Picard the truth about this, he has Picard go on some wild goose-chase to find android parts on a hostile planet where Picard could easily have been killed.
- Continuing the above idiocy, Shinzon wastes valuable time waiting aboard the Scimitar for hours before contacting the Enterprise, then mind-raping Troi when he should have been getting a blood transfusion from Picard ASAP.
- When the going gets tough for Shinzon, he decides to attack Earth for no reason whatsoever (He had no beef against Earth; it was the Romulans he hated. True, the Romulans who sided with him wanted to attack Earth, but Shinzon was under no obligation to them...he was the one in charge, not them!)
Yeah, he's a great villain.
To this day nobody has adequately explained to me what the fuck the Nexus is.
It was a plot device to get Picard and Kirk together so that Kirk could die.