The most immediate adjective that comes to mind regarding Boo Radley in Harper Lee's To Kill a Mockingbirdis solitary. Boo hasn't been seen outside of his house in years, creating much fodder for the gossipy townspeople and turning him into somewhat of an urban legend in the community.
As we learn more about Boo's history, it becomes apparent that he is also quite sensitive. It is suggested that Boo's strict Baptist father deeply traumatized his son and that Boo has become emotionally damaged from this treatment. Lee also posits that one reason Boo stays inside is that he's hurt by the town gossip about him. Through this information, we learn that Boo is quite sensitive to the judgement of those around him.
Boo's unseen presence in Jem and Scout's lives shows him to be a very curious person. After years of near invisibility, Boo begins to venture out to spy on the children. He appears genuinely interested in their lives and curious about their youthful misadventures.
When Boo starts leaving gifts for Jem and Scout, we see his the generous side of his personality. He leaves them various presents, including two small dolls carved to look like the children. In spite of the rumors about him, Boo proves to be a caring and generous soul.
In the climax of the novel, we learn that Boo is also incredibly brave; he emerges from nowhere to save Jem and Scout's lives from the wrath of Bob Ewell.
Although Boo is a solitary character, he...
also reveals himself to be sensitive, curious, generous, and brave throughout the novel.