This phrase literally translates to 'Two wrongs don't make a right'. It's used to express the idea that it is not acceptable to do something bad just because someone else did something bad to you.
Examples
- Spanish: Robarle a alguien que te robó sigue siendo robo. Dos males no hacen un bien.
- English: Stealing from someone who stole from you is still theft. Two wrongs don't make a right.