amistoso
friendly
amigo
friend
+
-oso
full of
Amistoso means friendly and can be thought of as amigo0 (friend0) + -oso1 (full of1), so it's someone who is 'full of friendship'.
adjective
- friendlyFriendly, kind, or showing goodwillEl perro es muy amistoso con los niños. // The dog is very friendly with children.