El que se ríe a sola de su maldad se acuerda

Spanish: Cuando José sonrió después de romper el jarrón, su madre le dijo: &#039;El que se ríe a sola de su maldad se acuerda&#039;.
English: When Jose smiled after breaking the vase, his mother told him: &#039;He who laughs alone remembers his own wickedness&#039;.

This is a saying rather than a slang term, which translates to 'He who laughs alone remembers his own wickedness'. It refers to someone who is amused by their own wrongdoings or mischievous acts.