Learn English – word that combines the meanings of “not practical” and “not useful”

Machiavellian describes someone who manipulates situations to their benefit, using human emotions when suited, and dropping them when not.

Revolutionary might be a good fit

when used as an adjective, the term revolutionary refers to something that has a major, sudden impact on society or on some aspect of human endeavor.

Usually Revolutionary means something that has completely changed the way people perform a type of action, rather than simply modifying or slightly improving it. For example, one could say the invention of the steam engine revolutionised transport.