硬汉 is always positive or neutral -- it means someone who is tough, resilient, and doesn't show weakness. The female equivalent would be 女汉子 (nǚhànzi), a tomboyish or tough woman.
memory
硬 (hard/tough) + 汉 (man) = a hard man. 汉 by itself can mean "man" or "fellow" (from 汉子, hànzi).
