Captain America isn't exactly a subtle superhero. That was by design: both in-universe and in reality, he was invented as a sort of walking propaganda tool, a living embodiment of America values and strength during the Second World War. He kind of had to be a guy literally decked out in the stars and stripes of the US flag.
So when you've got a superhero like that, you have to give him a similarly unsubtle villain to rail against. Well, Joe Simon and Jack Kirby certainly managed that by cooking up the Red Skull, Cap's nemesis who has - shocker - a scary red skull for a face. Plus he's a massive Nazi, just in case he wasn't terrifying and inhuman enough for you anyway.
The Red Skull is Captain America's most famous enemy, recurring through the comics since his first appearance in the thirties and figuring into both animation and live action adaptations of the character, most recently appearing in Captain America: The First Avenger, played by Hugo Weaving.
He's not particularly subtle, but there's actually a lot going on with this particular supervillain you might not be aware of. There's his power set, his family history, his relationship with a certain infamous Adolf, and his previous (inexplicably Italian) movie appearances...all figure into the ten things you didn't know about the Red Skull.