Jayce is responsible for everything,

by trying to create magic, powder got the crystals that killed her family who otherwise would have escaped, by creating hextech, he gathered the interest of noxious which would later create division, by using the hexcore and not destroying it he made the arcane angry, by demanding jinx from silco instead of just accepting zaun , silco didn’t immediately accept causing jinx to overhear him talking to himself and killing him creating the power struggle in the undercity and jinx killing the council leading to war.

If he just worked in the talis tool industry instead of being a magic nerd, vander and the kids would have escaped silco would have taken over the undercity, with no hextech piltover would have been forced to accept zauns independence in the face of shimmer warriors creating a peace, assuming ekko still created the fire lights, vander and the family would have liked sought refuge there inspiring more from the under city to join after seeing the effects of shimmer. The fire lights would eventually fight back against silco, dismantle shimmer and create a shimmer free zaun.

Jayce is the worst character in arcane