Watchmen, despite what you may be led to believe by Zack Snyder's less-than-faithful 2009 adaptation, was never a comic of violence or gore and instead relied on mind games and shocking acts of depravity to detail the battles (both internal and otherwise) between the series' heroes.
This self-control displayed by Dave Gibbons and Alan Moore made their haunting series of splash pages detailing the destruction of New York all the more impactful, and have gone down as some of the most haunting images from the now-legendary series.