General opposites:
* Tímido: Shy, timid
* Cohibido: Inhibited, bashful
* Recatado: Reserved, modest
* Cauteloso: Cautious, careful
* Temeroso: Fearful, timid
Opposites in specific contexts:
* If "atrevido" refers to someone being bold in their actions: Prudente (prudent), cauto (cautious), conservador (conservative)
* If "atrevido" refers to someone being bold in their style or appearance: Discreto (discreet), simple (simple), sobrio (sober)
It's important to consider the specific situation when choosing the opposite of "atrevido."