Arma de doble filo is a fantastic Spanish idiom that literally translates to "double-edged sword". It's used to describe something that has both positive and negative consequences, just like a sword that can cut both ways.
In the song, Enrique Iglesias uses this powerful phrase to describe a lover who is both a source of immense joy and deep pain. It perfectly captures the complicated nature of a passionate relationship filled with highs and lows, making it a very memorable expression.
Enrique Iglesias and Maria Becerra sing about a love that's like a high-stakes poker game. They see life as a gamble where you have to bet everything, just like they did with their relationship. They admit it had its "altos y bajos" (ups and downs), but they never took the easy way out. Now, it seems they're on different paths—"Tú escogiste un camino y yo la vereda" (You chose one path and I the other)—but the connection is still there, just in a new way. It's a relationship that life is putting to the test.
The best part is their attitude towards what other people think. They basically say, let everyone else laugh and call them idiots. They don't care. He sings that there's "nada más fuerte que lo de nosotros" (nothing stronger than what we have). He even defends her when people talk, calling her an "Arma de doble filo" (double-edged sword) and telling the gossips to get lost. In the end, even if she steps on his pride in public, he can't do anything about it. Why? Because, as he says, "Mi corazón es tuyo" (My heart is yours).