Verses with the word transgressor in the Old Testament (3 verses):

Proverbs 21:18
The wicked shall be a ransom for the righteous, and the transgressor for the upright.

Proverbs 22:12
The eyes of the LORD preserve knowledge, and he overthroweth the words of the transgressor.

Isaiah 48:8
Yea, thou heardest not; yea, thou knewest not; yea, from that time that thine ear was not opened: for I knew that thou wouldest deal very treacherously, and wast called a transgressor from the womb.