Positive:
* Abolitionist: This is the most fundamental descriptor, highlighting his commitment to ending slavery.
* Zealous: Brown was passionate and unwavering in his beliefs.
* Courageous: He was willing to risk his life and face great danger to fight for his cause.
* Idealistic: He believed in a just and equal society, even if it meant resorting to extreme measures.
* Radical: Brown's methods were considered radical even for his time, but he believed they were necessary.
* Charismatic: Brown was able to inspire others to join his cause.
Negative:
* Violent: Brown's use of violence is often seen as a major flaw.
* Fanatical: Some argue that Brown was driven by an extreme and uncompromising belief system.
* Terrorist: Brown's actions, especially the raid at Harper's Ferry, are considered acts of terrorism by some.
* Ruthless: His willingness to kill, even in self-defense, is seen as a sign of cruelty.
* Messianic: Brown saw himself as a divinely ordained leader, which some find troubling.
* Unrealistic: His belief in a quick and violent overthrow of slavery is seen as unrealistic and ultimately harmful.
Neutral:
* Controversial: John Brown's actions and beliefs are highly debated and there's no easy consensus on his legacy.
* Complex: He was a multifaceted figure with a complicated history, making it difficult to categorize him simply.
* Ambiguous: His actions were both heroic and disturbing, leaving a lasting ambiguity about his character.
Ultimately, the best adjectives to use depend on the context and the specific aspect of John Brown's life you're focusing on.