Archer thinks the refusal to kill is naive and the ideal is doomed. But then again, this is also him:

[hider=Archer]

"But I did not care, so long as I could save people.
Emiya Shirou could not fulfill his oath.
So I thought it would be fine if I could become a guardian to take part in stopping humanity's destruction."

[img=http://lparchive.org/Fatestay-night/Update%20216/51-UBW15-01-121.jpg]

All they do is clean up after humans. They take what has been done and nullify it with their powers."

"They do not save people. All they do is eliminate harmful people, without distinction of good or evil.
They do not save people in despair. Instead, they eliminate people in despair in order to save others who are enjoying life.
It's so ridiculous. How am I different from before?"

[img=http://lparchive.org/Fatestay-night/Update%20216/52-UBW15-01-124.jpg]

He relied on a greater power since his powers alone were not enough.
But it ended up being the same.
He thought the power would make his wish come true, but it only made him do the same things on a greater scale.

"…Archer. You have repeated such a thing forever…?"

"I got used to it. Humans repeat things. The strong feed on the weak, regardless of what age we're talking about. And I came to realize that it is the most efficient way to prosper."

[img=http://lparchive.org/Fatestay-night/Update%20216/53-UBW15-01-128.jpg]

That is where he ended up.
A being that repairs the damage caused by human desire.
Guardians do not save people. Rather, they eliminate those who cannot be saved as if they never existed.

[img=http://lparchive.org/Fatestay-night/Update%20216/54-UBW15-01-131.jpg]

Over and over.
For many times, he saw people nearly destroy themselves through their own actions, and he burned them down like trash each time.
"Save as many people as possible".
The man became a hero with that one wishbut in the end, he could not make it come true even once.

[img=http://lparchive.org/Fatestay-night/Update%20216/55-UBW15-01-135.jpg]

[img=http://lparchive.org/Fatestay-night/Update%20216/56-UBW15-01-137.jpg][/hider]

Though he's trying again anyway, because of the rest of the route. XD