madman

a man who is seriously mentally ill and behaves in a strange or violent way

locura, demente (hombre)

Collocations madman on the loose

• The police are looking for a dangerous madman.

  La policía está buscando a un peligroso demente.

used to describe someone who is behaving in an extremely foolish or silly way, especially when they are doing something dangerous or risky

tonto, loco (en broma)

Collocations madman with a plan

• He's a madman to drive in this weather.

  Es un loco por conducir en estas condiciones.