Do not return evil for evil, vengeance is the Lord's

Scripture references

Matthew 5:38–42 (ASV)

38Ye have heard that it was said, An eye for an eye, and a tooth for a tooth: 39but I say unto you, Resist not him that is evil: but whosoever smiteth thee on thy right cheek, turn to him the other also. 40And if any man would go to law with thee, and take away thy coat, let him have thy cloak also. 41And whosoever shall compel thee to go one mile, go with him two. 42Give to him that asketh thee, and from him that would borrow of thee turn not thou away.

Romans 12:17–21 (ASV)

17Render to no man evil for evil. Take thought for things honorable in the sight of all men. 18If it be possible, as much as in you lieth, be at peace with all men. 19Avenge not yourselves, beloved, but give place unto the wrath of God: for it is written, Vengeance belongeth unto me; I will recompense, saith the Lord. 20But if thine enemy hunger, feed him; if he thirst, give him to drink: for in so doing thou shalt heap coals of fire upon his head. 21Be not overcome of evil, but overcome evil with good.

1 Peter 3:8–12 (ASV)

8Finally, be ye all likeminded, compassionate, loving as brethren, tenderhearted, humbleminded: 9not rendering evil for evil, or reviling for reviling; but contrariwise blessing; for hereunto were ye called, that ye should inherit a blessing. 10For,

He that would love life,

And see good days,

Let him refrain his tongue from evil,

And his lips that they speak no guile:

All Simon Zhao ever wanted, right from when he was just a boy, was vengeance against the man who violated his mother. This hateful quest remained in Simon until he met God and things changed!
Chen’s daughter died few days after she was cruelly beaten by an ill-tempered woman. But contrary to common culture of revenge, Chen asked that his daughter’s murderer not be punished. His only request was that she be warned so no other child suffers his daughter’s fate.
After Ben's death, the Townsends were urged by many to sue the physicians who attended to and under treated their son. But even with an assurance of victory in the courts, the Townsends chose forgiveness; they chose to not be bitter or take revenge.
Once when Brother Yun was arrested, he was horribly and shamefully treated. While he was tempted to lash out, the Lord stopped him and reminded him to "not repay anyone evil for evil."