Bad guys are confident and self assured.

坏小子总是自信并且自我感觉良好。

youdao

His manner was self-assured and brusque.

他的举止自负而且粗鲁。

《柯林斯英汉双解大词典》

The oldest tends to be self-assured, responsible, a high achiever, and relatively serious and reserved.

最年长的那一个往往自信、负责、成绩优异，也相对严肃和保守。

youdao

The aristocracy might be selfish and sometimes cruel, but it's also witty, cultivated, mannerly and effortlessly elegant and self-assured.

WSJ: Theodore Dalrymple on the Secret Appeal of Downton Abbey

Michelle was never shy, but she has become even more confident, outgoing and self-assured as she has lost weight.

CNN: Why you really should get 'Fit By 40'

Though Lenny's customers run the age gamut from adolescent gamines to sexy seniors, her devotees are widely regarded as mature and self-assured.

NPR: Lenny's Rise From Garage To Brazil's Bikini Queen