If you take a classical/koine Greek class, the first words you learn for “good” and “bad” are “kalos” and “kakos,” which also mean something like “beautiful” and “sh*tty.”
The Septuagint decided to translate certain kinds of good and bad things with two different Greek words: “agathos” and “poneros.” These also mean something like “admirable, excellent, suited to the purpose, fertile for agriculture” and “toilsome, painful.” Agathos is good as in the seed falling on good ground, in a good heart. Poneros is bad, as in a bad decision for bad reasons, that makes life worse for you in the long run. “Agathos” is also used to express righteousness. In Greek literature, someone who is “agathos” is noble in character, the opposite of someone who is “kakos.”
There are some other Greek words for good and bad, but “agathos” comes up in today’s second reading at Mass in the OF, 1 Peter 3:18-22. We’re not actually asking God for a “clear” or “clean” conscience, but for a good, righteous conscience that bugs us and keeps us out of trouble.
(We also have the word “makrothymia,” which doesn’t mean “longsuffering” or “patience” the way we use it, even though that’s how it’s translated this week. “Thymia” is passion, temper, spiritedness, the way a bold warrior acts. It comes from “thymos,” which also means spiritedness, and usually a sort of righteous anger. “Makrothymia” is the quality of biding a long time before deploying the thymia and making havoc. “Slow to anger” is more to the point than “longsuffering.” In the Septuagint, Isaiah 57:15 has God promising to give makrothymia to the lowly of soul/mind (“oligopsychois”), where the Hebrew promises to “revive” the spirit of those with a humble spirit. So having makrothymia is a dynamic quality, promising action.)