Turtlenecks are a fashion that for most just doesn't work. It just ends up looking silly and scarfs are much more awesome anyways. However a select few have been known to sport the turtleneck and sport it well.
They are evil people. You know they are evil people because they are either very handsome or very beautiful or sometimes and somehow both.
Only they can don the turtleneck and not look incredibly stupid. Perhaps
the reason why is because turtlenecks draw attention to your ugly mug
(Seriously bottles are so much cooler). Since good looks has been scientifically proven to be correlated with being evil according to mad scientists it follows that those who wear turtlenecks and can get away with it must be incredibly evil. Also those who wear the turtlenecks
of evil prefer tea over coffee and it better damn well come in a cup and saucer. Sometimes ugly evil people wear turtlenecks too. One might mistake these people for good people who just lack fashion sense.
However the reality of the situation is that these people are so evil
they just don't care that they directing attention to their hideous
mug (Even cans are better.) Black turtlenecks are especially evil.
Main example would be Johan Liebert.
He wears turtlenecks a LOT and is pretty darn evil.
Killua from Hunter x Hunter is another possible example.
He may not be a "bad guy" per se but he is an assassin.
He wears turtlenecks.
Shizuku from Hunter x Hunter is another example.
She's a member of the Phantom Troupe that steals and kills indiscriminately.
The Despicable Me dude
Madara Uchiha from Naruto. He wears a turtleneck underneath his Akatsuki cloak.
Rubel from Claymore. He may or may not be evil but he's definitely shady.
Jack Nicholoson in the Shining wears a turtleneck here
and look he's evil.
Dr.Evil from Austin Powers wears a turtleneck
There should be more examples but I can't think of them right now.
Ok here's another
Both from Harry Potter.
Michael Fassbender as Magneto