Vash wasn't perfect, but neither was Gilbert. Prussia was covered in scars from all the years...centuries...he's been around. Switzerland's body was a landmine of old wounds. They weren't perfect, but they tried to be.
Gilbert tried not to flinch every time Vash fired his guns. He fought the urge to cry whenever the Swiss would raise hia hand or voice. The Prussian would tremble with need to hide whenever someone knocked on the door. Gilbert even tried not to stab anything that entered his room at night.
Vash knew he shook whenever Gilbert played the piano. He flinched every time the Prussian would take off his clothes. THe Swiss would have a panic attack when Gilbert would go missing. Vash tried so hard not to shoot everyone crossing the border for the Prussian's sake.
They weren't perfect though they tried to be, even though they didn't need to.