I think the worst thing a friend can do to another is doing nothing to save him or her when he or she is in a big trouble. Friends should help each other during a hard time. When one of my friends didn't know how to do his homework and I helped him and he was so happy just like a very hungry man gets lots of food to keep him alive because the teacher in school is very fiendish. So I felt happy too. When a big and strong dog was chasing me and I was very terrified at that time (I fear dogs very much when I was 6~9 years old). Just then, my best friend came and kicked the dog and the dog went away. I was so thankful to him and I thought if he gets in trouble, I will do everything to help him, even if I will get in a bigger trouble. And if I am in a big trouble and no one come and help me, I'll be very unhappy and may be mad at the friend which was near me at that time. I don't want my friends feel bad and I don't want to feel bad. So I think the worst thing a friend can do to another is doing nothing to save him or her when he or she is in a big trouble.