Silco was a monster who used monstrous methods. He used child labour, peddled drugs that utterly ruined people mentally and physically, and ruled the underworld with fear and an iron fist. He killed and ruined the lives of countless people to achieve his dream of an independent, sovereign Undercity.
And he so very nearly succeeded.
But for one thing: his precious Jinx.
When faced with the corpse of his underling's son, his response is a cold, unconvincing, boilerplate statement of sympathy, immediately followed by the fact that the child should have been glad to die for a good cause. He doesn't really care. Why would he? He's thrown so many others to the wolves for the sake of his plans.
And he has everything he's been working towards for decades handed to him on a silver platter. Jayce - arguably the single most influental member of the council at that point - agrees to everything. Independence. Sovereignity. Access to the Hex Gates and the economic opportunites they present. A signed peace. And, incredibly, the Council is willing to go along with it.
There's just one more person he needs to throw under the bus. One more, among however many thousands who's lives he's ruined and ended. Jinx herself.
And he can't do it. He even tries to assume resonsibility for Jinx's actions - ironically one of the only things he's not responsible for, given how much of a loose cannon she is. But that improves impossible, and Silco finds himself backed into a corner: sacrifice his dreams, or sacrifice Jinx. He chooses to sacrifice his dreams.
And so, the tragic irony of Silco is that he was unable to realize the outcome of his decades-long plans...because he was not quite ruthless and monstrous enough.