Reckless
 

dictionaries say
temarario
imprudente
atronado

To me temarario means daredevil which is reckless but often in a positive way.
In English imprudent means using bad judgement which can mean reckless, but
can also mean unwise.

Is there a better term in Spanish?

You mentioned the adjective reckless but for whatever it's worth I've heard the adverb recklessly as a tontas y a locas. Hope it helps

Sure tonto y loco are close. Silly and crazy combined is reckless. I was thinking peligrosamente inprudente, but that's a mouthful.

DRAE says which doesn't sound very positive.

So, I suppose arriesgado or atrevido would be a better translation for daredevil (as an adjective) than temorario.

alocado maybe