"The good that I would do, I do not do; the evil that I hate, that is what I do." St. Paul

"Do not do evil in order to brinig about good." St. Paul

If you want some specificity in the details, you could also look into the Donatist schism and the concept of purity in the church with Augustine' attempt to reconcile this vis-a-vis the Catholic Church. There is a strong discussion about what 'good' and 'evil' entails - Augustine believed that coercion should be used to force the schismatics back to Catholicism by claiming the parable of the supper is verification that salvation is only possible through the Church. Paul is another example of this, but Aug also discussed the other parables including Dragnet and the Tares where both good and evil were invited to the wedding in as much as wheat and tares grow together. Is the suggestion by Augustine that ultimately forcing Donatists to align themselves with the Catholic Church ethical - considering it did ultimately lead to their violent demise - inasmuch as it is ethical for the Donatists to claim no validity in religious practice unless the practitioner clearly exemplified a rigour of extreme purity? Also, is there any real validity in Biblical hermeneutics?

I recommend Against the Donatists.

Some tips:
"Evil" is a word that used to mean being of two minds on a subject, a synonym for ambivalent.
"Good" can be thought of as the summary assessment of actions that survived.