How? The tutorial used to be on here, but the old site is gone now.

Could someone give a perfect kill counter sample?

What do you mean by a "perfect" kill counter?

Instead of using something like:
C: Kill Score: 1
A: Set Kill Score: 0
A: Give the kill bonus

There's a system that will work better, with more than one kill at a time. It's usually used in defenses. There used to be a tutorial for it on here.

Well, its not completely gone. Here is the link to that topic in an archive: Kills to cash - perfect

Here is Thermo's demonstration map.