Oh, I understand it all right...
A bully loves to kick people when they are down, whereas a strong person would pick them up.
A bully will gloat even at the slightest hint of success, whereas a strong person simply accepts it and moves on to the next challenge.
Being a bully means that you’re picking on someone because you want attention. You feel that being “popular” or having status will bring you friends.
Being strong means to get back up after someone has punched you with an insult or humiliated you. You keep going without trying to use someone’s weakness against them.