How to Say "reckless" in Spanish
The Spanish word for “reckless” is “animal” — B2 level.

Examples
¡Qué animal! Rompió el jarrón por no mirar.
How clumsy (or 'what an idiot')! He broke the vase because he wasn't looking.
Este conductor es muy animal, va a 140 km/h en la ciudad.
This driver is very reckless, he’s going 140 km/h in the city.
Informal Adjective Use
When used this way, animal is often used as a descriptive noun/adjective that usually means 'reckless person' or 'oaf' and is applied directly to the person being criticized.
Using the literal meaning
Mistake: “Un policía le dijo que era un animal (expecting him to be literally a non-human creature).”
Correction: This is almost always hyperbole, meaning the person is acting wildly or irresponsibly, not that they are literally a beast.
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