Actually it has been stated that an edge that combats only one specific thing will prove quite effective (say the anti-kot edge), whilst ones that combat lots of things (say the anti-ko edge) will be less effective.

Beyond that, any countermeasure is generally of greater magnitude than a standard skill/Edge/whatever because it's reactive rather than proactive.

For example, let's say you have an anti-knockout Edge. Even that has to be pretty good against knockout, because many opponents (a majority of PCs and a large majority of NPCs) will never attempt to knock you out, and the Edge is absolutely useless against them. Compare this to "I am good at knocking people out.", which the user can use against most opponents. Therefore, the countermeasure Edge has to be one or more of:

1) Very good against its counter.
2) Easy/cheap to obtain.

valguarnera@carrionfields.com