Basso Profundo is an incredibly deep and rare voice type, but we fortunately have some examples due to the popularity of the voice type (many times abused).
Similar to Bass but in a lower extense, Basso Profundo has a very rich and "big" timbre and really shines in the low end of their tessitura. It's quite impressive to think they differ from a Baritone (which would still be a medium-low voice type) the same way a Baritone differs from a Tenorino.
Contrary to what it's intended in classical music, Basso Profundo does not mean "Dramatic Bass" (that's just a subtype of Bass) and is also divided into 4 categories (yes, Dramatic Basso Profundo exists and we are not afraid of it).