You should always pay back money you owe to others.
Brock borrowed a good amount of money from his friend a long time ago and his financial situation has improved significantly.
Brock wants to consider paying his friend back.
Brock pays back his friend in full with a little extra for helping him out.
Brock decides to never pay back his friend and simply moves on.
Brock is seen as someone with integrity and his relationship with his friend strengthens.
Brock's friend thinks Brock is a dishonest person and is no longer friends with Brock.