IPA: /ɪnˈfeɪməsli/
KK: /ɪnˈfɛməsli/
In a way that is well known for a bad quality or deed.
The criminal was infamously known for his daring heists.
Infamously → It is formed from "in-" (meaning not) and "fama" (from Latin, meaning fame or reputation) and the suffix "-ously" (meaning in a manner of). The word "infamously" means in a manner that is not famous, often referring to being known for negative reasons or disgrace.
Think of 'not famous' ('in-' means not and 'fama' means fame) to remember that 'infamously' describes someone known for bad reasons.