This is the 1343rd most frequent Russian word.
хорошим
"Хорошим" means "good" in the instrumental case.
Here, "хорошим" is used as an adjectival participle in the instrumental case to describe the noun "другом" (friend).
Он всегда был хорошим другом.
He has always been a good friend.
In this sentence, "хорошим" is in the instrumental case, serving as a predicate adjective with "становиться" (to become).
Становиться хорошим человеком — это цель многих.
Becoming a good person is the goal of many.
Here, "хорошим" is in the instrumental case, used to describe the hypothetical noun implied in the discussion context.