2 former coworkers of mine who always the smartest person they know. One of em lives alone and you can tell he's never lost an argument (with himself in his head) and anytime he tries to back up his opinion it's always the same "it's dumb, it's stupid, it doesn't make sense it's not LoGiCaL". But anytime you try to chime in...he talks over you.
The other is one of those "I read both sides of the story so I know far far more than you"...who was a one of those reddit knowitalls.