In clinical terms, the Professor is a straight-up narcissistic psychopath. The book describes him as being very short, frail, and ugly-looking, but the dude is still totally convinced that he's better than everyone else. He constantly talks about how the people around him are him are mediocre, even while the "lamentable inferiority of the physique [is] made ludicrous by [his] supremely self-confident bearing" (4.6).
He has absolutely no real accomplishments to show what a genius he is. The only evidence he seems to need, though, is his own certainty that he's a great man. Ever met someone like that? They're pretty tough to be around.
The Professor tries to prove his importance to the world by carrying a powerful bomb in his jacket. His ability to kill dozens of people makes him think that he's a god as he walks down the street, because he knows that no police officer would dare come anywhere near him. Because he's a dude who's obsessed with being strong, he hates the weakness that he sees in everyone else. He even tells Ossipon that he wishes there would be a huge "extermination" (13.7) of all the weak and mediocre people, a wish that creepily foreshadows Hitler's (obviously wrong) justification for the Holocaust.
The Professor is basically a symbol of the self-obsession and individualism that was already becoming pretty common in the early 1900s. Compared to any other character in this novel, the Professor might even seem like he's the most well-adapted to the modern world. Unlike Verloc, he's not lazy. Unlike Winnie, he's not willfully ignorant. And Unlike Stevie, he's not compassionate. Dude looks out for numero uno.
But again, Conrad's not giving us a role model. The Professor's got a huge Achilles heel: he's a total diva, and he needs the world to recognize him for the great man he is.
The Professor might come across as pretty tough, but he's just a little pipsqueak with a bomb in his pocket. His sense of greatness is a total fantasy. He wears shabby clothing, lives in a tiny apartment, and doesn't have any friends. No matter how important he might think he is, he'll never stand out among the millions and millions of people who live in London.
He thinks he can make the world afraid of him, but he's tortured when he sees the crowds moving through London's streets "like locusts, industrious like ants, thoughtless like a natural force" (5.2). Sure, the Professor loves to think about other people as insects, because this makes him feel like he's better than them. But he also needs recognition, and insects can't give him recognition because they're totally unthinking.
The book ends on an ironic note, comparing the Professor himself to an insect, or at least a pest: "He passed unsuspected and deadly, like a pest in the street full of men" (13.56). Yowch. The Professor just got told.
Pretty much every character in this book represents a certain worldview, and the Professor is no exception. And just like every other character, he's got a huge blindspot. He thinks he's got life figured out because he's willing to die to make his point. The problem is, though, that the world just doesn't care. Through the Professor Conrad shows us how full-blown selfish ambition is not a worthwhile way to live in the modern world. It might make us feel powerful at first, but the truth is that there's no point in trying to be better than other people… because the world just doesn't care.