Carácter literally means "character", but in this song, it takes on a deeper meaning of one's unchangeable, innate "nature".
The song retells the fable of the scorpion and the frog. When the scorpion gives its fatal sting, dooming them both, it explains, "no he podido evitarlo, es mi carácter" (I couldn't help it, it's my nature). This word is the key to the song's dark, philosophical message about powerful instincts that can defy all logic.
Ever heard the tale of the Scorpion and the Frog? Charly García brings this dark fable to life in his song. A scorpion asks a frog for a ride across a river. The frog is hesitant, naturally fearing the scorpion's deadly sting. But the scorpion is persuasive. It uses 'logic' to convince the frog, arguing, 'If I sting you, you'll die, and I will drown. That's not logical!' Convinced by this argument, the frog agrees to help.
Of course, there's a tragic twist. In the middle of the river, the scorpion stings the frog. As they both begin to sink, the frog cries out, asking why. The scorpion's chilling reply gets to the heart of the song's message: 'I couldn't help it. It's my character.' This song is a powerful and cynical look at our unchangeable nature. It's a cautionary tale suggesting that some instincts are so deep that they override all logic, reason, and even the will to survive.