Blubber!
A b word meaning helpful is beneficial.
A b-word is any of a group of words beginning with B which may be considered rude or vulgar.
bauble
Another word for kindly beginning with 'b' is benevolent.
Backrushes.
Ballerina is one 9-letter word beginning with B and ending with A.
Bland.
because
Botany.
Bureau or badminton...bonjour
Bloody
The word is bulb.