Stupidity: When the Gorn attacks Archer, one of the MACO officers raises his weapon to fire, but fears hitting Archer, so he doesn't shoot. But then he attacks the Gorn with the butt of his weapon. He was close enough to hit him, he could have just stood over him and fired without fear of hitting Archer.
Stupidity: The last remaining Xindi, in desperation, attempts to release the virus over the fan, despite the virus not being fully ready. However, it seems the only reason he didn't release the virus at that time was he had to seek cover from Archer and T'Pol shooting at him and to start shooting back at them. However, he had plenty of cover from the rooftop stairwell, which was right next to the fan, and he had enough time to dump out the contents over the fan.