Canallas translates to "scoundrels" or "rascals." It's a strong, somewhat old-fashioned word that isn't heard in everyday conversation or every song, making it quite memorable.
In this song, the singer uses it to describe the ex-boyfriend's character, singing, "El olfato para canallas" (a nose for scoundrels). This implies she has a keen sense for identifying untrustworthy people, adding a sharp, assertive tone to her warning.
Have you ever been the protective friend who has to pick up the pieces after a bad breakup? In "Pero Yo Sí," Argentinian artist Yami Safdie sings from that exact perspective. The song is a powerful warning to an ex-partner who hurt her friend. The speaker is furious, telling this person they'd better not cross her path on the street. She reminds him that she only gave him a couple of simple rules: take care of her friend and don't make her cry. He failed miserably.
The speaker points out that while her friend might eventually forgive and forget the pain he caused, she never will. The title itself, which translates to "But I Do," captures this feeling perfectly. She was the one who saw her friend cry, question what she did wrong, and suffer through sleepless nights. He wasn't there for the aftermath, so he doesn't get to just come back now that he regrets it. It's a fierce anthem about friendship and holding people accountable for their actions, even when the person they hurt is ready to move on.