In Dragonlance there is a character called the Kingpriest, he is the epitome of lawful good...
-At the onset of his reign he created an order of "Knights", and tasked them with rooting out worshipers of evil gods and those who performed evil deeds.
-Years later he decided that worshipers of Neutral gods are just one step from Evil, because sometimes they perform Evil acts. His knighthood then began rooting out the worshipers of Neutral gods.
-Years later he decided that Wizards were evil, even if they followed the God of good magic. His knighthood then began destroying wizards in the Lost Battles.
-Years later he decided that if you don't worship the good gods in the way that he believes is the way they should be worshiped, you are a heathen and should be eliminated. His knighthood then began eliminating those who worshiped the good gods in ways that were different from his church.
-Near the end, he decided that evil acts are not the only evil, evil thoughts are also evil waiting to become deeds, so he began drafting edicts of "Thought control" to make sure that people weren't even thinking of "evil" things.
He wasn't being evil, he was being lawful good. Lawfully the only way to worship/act was the way he determined is the right way, and if you were doing it any other way, thinking any other way, then you were violating the "Laws of the Gods" and were therefore not good.
So yes, a "Good" character can be the enemy, because at its most extreme good is indistinguishable from evil. You just have to reflect on how someone could perform "Good" acts that would harm others.
(Yes, I'm leaving a lot out of the story of the Kingpriest. They're amongst the best Dragonlance books written and I don't want to spoil the story if there is someone who hasn't read them but might want to)
-At the onset of his reign he created an order of "Knights", and tasked them with rooting out worshipers of evil gods and those who performed evil deeds.
-Years later he decided that worshipers of Neutral gods are just one step from Evil, because sometimes they perform Evil acts. His knighthood then began rooting out the worshipers of Neutral gods.
-Years later he decided that Wizards were evil, even if they followed the God of good magic. His knighthood then began destroying wizards in the Lost Battles.
-Years later he decided that if you don't worship the good gods in the way that he believes is the way they should be worshiped, you are a heathen and should be eliminated. His knighthood then began eliminating those who worshiped the good gods in ways that were different from his church.
-Near the end, he decided that evil acts are not the only evil, evil thoughts are also evil waiting to become deeds, so he began drafting edicts of "Thought control" to make sure that people weren't even thinking of "evil" things.
He wasn't being evil, he was being lawful good. Lawfully the only way to worship/act was the way he determined is the right way, and if you were doing it any other way, thinking any other way, then you were violating the "Laws of the Gods" and were therefore not good.
So yes, a "Good" character can be the enemy, because at its most extreme good is indistinguishable from evil. You just have to reflect on how someone could perform "Good" acts that would harm others.
(Yes, I'm leaving a lot out of the story of the Kingpriest. They're amongst the best Dragonlance books written and I don't want to spoil the story if there is someone who hasn't read them but might want to)