know or seem to know everything
omniscient - all-knowing
Like the similar ‘omnipresent’ and ‘omnipotent', the term ‘omniscient’, derived from the Latin word for 'all knowledge’, can only strictly speaking be applied to a deity. However, it is most commonly used in relation to somebody or something that seems to be all-knowing, or as a warning of the dangers of mistakenly thinking that about them.
We should be prepared to challenge the opinions of experts rather than simply presuming that they are omniscient.
That tech company has become so omnipresent and powerful that people might be forgiven for mistakenly presuming that they also have omniscience.
The dictator of that totalitarian regime likes to portray himself as omniscient and uses the state-controlled media for that purpose.