At the start of the Vinci Massacre, the gunfire heading into Amarilla's cookhouse causes a massive explosion on the top floor. That's all well and good, but either due to safety or to cut costs, the explosion is blatantly CGI. Bad, bad CGI. The lighting and general positioning of the explosion just doesn't fit with the live-action elements, making it painfully obvious that it's been cobbled together in post. The smoke, the fire, it all looks laughably stock and serves as a brief distraction in an otherwise highly precise scene.