Note: These distinctions are how Leon subconsciously groups people. Their status can move around in his mind.
FRIENDS
Protected: People Leon feels that he has to take care of; he's responsible for their safety, and will feel the most guilt if they're hurt.
Sohma Kagura
Clark Kent
Eileen Galvin
Yukito
Equals: People who are around Leon's equal in knowledge/ability; they can take care of themselves, as well as help him out.
Javert
Ichimoto Ren
Kuhdo Yohji (roommate)
Alec Trevalyan
Lord Mark Pierre Vorkosigan
Archer
Leaders: People with more knowledge/ability than Leon; those who are obviously in positions of authority.
Captain Hitsugaya Toshiro
Matsumoto Rangiku
ENEMIES
Those who are trying, in some way, to harm Leon or those he considers friends.
Nurses, doctors, monsters, etc.
Albert Wesker
William Birkin
OTHER
People who don't fit into any of his above categories; usually people who aren't trustworthy, but aren't actively trying to harm him, either. These people confuse the hell out of Leon.
"Admiral" Zex