The noun 'gang' is a standard collective noun for:
The collective noun is a gang of bikies.
The most common collective noun is a bunch of crooks. Then there is a gang of thieves, a gang of robbers, so why not a gang of crooks.
There is no specific collective noun for the word kidnapper, in which case a noun suitable for the situation is used; for example, a band of kidnappers, a gang of kidnappers, etc.
Gang
There is no specific collective noun for the noun guerillas. A collective noun for a similar group can be used, such as a troop of guerillas (a troop of soldiers) or a gang of guerillas (a gang of hoodlums), depending on your opinion of guerillas.
The collective nouns for prisoners are a pityof prisoners, a gang of prisoners.
The collective nouns are a herd of bison and a gang of bison.
The collective nouns are a gang of hooligans or a mob of hooligans.
Collective nouns for workmen are a crew of workmen or a gang of workmen.
The collective nouns for workmen are a crew of workmen and a gang of workmen.
The collective nouns for laborers (UK spelling labourers) are:a gang of laborersa crew of labourers
The standard collective noun is a gang of criminals.