Relativity of ethics
What is good or bad? Are they set in stone or is something that is bad for you possibly good for someone else... If a parent steals bread from a bakery to feed their starving child, this is obviously bad for the baker, however, it is good for the parent and child. This is the concept of moral relativism, where we use the words good and bad as common terms, but their meaning is actually relative to the individual at that point in time.
A famous example of this is Star Wars. In Episode IV, Luke Skywalker and the Rebels go out to defeat the Empire and blow up the Death Star, hes treated as a hero, however, flip the perspective... Imagine an Imperial officer coming to work on the Death Star simply to pay his mortgage and feed his newborn baby... It begs the question, is Luke doing good when he launched the proton torpedo blowing up the Death Star or was the Imperial officer doing bad when coming to work to feed his newborn child? Isn't the Star Wars Saga just a story about a group of heartless terrorists? Or a bunch freedom fighters?
Some people try to simplify this concept by simply believing in the moral standards of a book, however rules like "thou shalt not steal" doesn't work in our bread stealing parent analogy. But our energy frugal brain likes the concept as it fits nicely on a shelf in our brain. In fact the concept of what is good or bad depends on a wide range of element, see below.
The Definition of Good
In this galaxy, not so far away... under our feet in fact, we all stand on earth. We all drink the same water, and breathe the same air, if someone truly thought their aim was to do good, the only 100% good, would be what is in the common good for all. i.e. their actions would primarily be involved in protecting our common environment as this is the foundation of our collective need as define by Maslow's Hierarchy.