Watts up Larry?
I'm going to assume that a Watt of power for a laser you're referring to is the input power. A Watt output would not only be blinding but possibly hazardous. A 5mW (.5% of a Watt) green laser pointer would rock your retina's world for a while, assuming a direct hit. It might not be perminent but it would certainly be specacular.
Ultimately it depends on the intensity at the target, not the aperature but a well columnated laser should be spectacular for a good distance. Modulate it at some neurologically significant frequency and you've got a dazzler.