I have a pair of MCs but I'm gonna focus on Lucifer since he is the one who has something to do with the villain, while Amèlia, the number 1 MC to say it somehow, is basically who observes the things through human eyes.

Lucifer knows very well the big bad, I'm not gonna say much about it bc spoilers but basically when he was created there weren't much more people there so yeah, he knows them a lot. And this is why he hates them; the villain is a dictator and Lucifer the revolucionary angel that opposed them so basically they have a hate each other a lot.

this is the Supreme Angel, the villain

My series is still very young so my MC doesn’t know who the big bad is. But, since the beginning he knows that the world now divided into at least 2 factions, he knows there is a big bad somewhere. I don’t know yet how he will meet big bad but it’s gonna be in a fight.

And to the promotion:

Darzsa knows the big bad and first hears of her in the first few episodes and meets her fairly early on. Their first encounter (at a seance) was a joy to write and its a true battle of wits that almost ends in violence. Great fun.

ugh, I want to share mine so baaad, but it's still too early hehe
anyways, my MC can sympathize with Kerren a bit, but instead of a creepy guardian, my "current" big bad was his Dr. Frankenstein of sorts

My MC knows the big bad at this point, and has fought him before, but things have yet to escalate to true enmity. Currently the Big Bad is just a villain they ran into once, and the MC has no idea how things will change.

Classic Fantasy doesn't have a big bad, honestly. There are antagonists of varying importance, but there is not "That One Dude to Defeat". It's about adventure, not plot.

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The Ghoul doesn't have a very clear main villain, and Julian (the MC) didn't know any of the characters that could be labeled as antagonists beforehand. Of these characters, the titular ghoul "knew" Julian, as well as a near mindless thing can know someone, but it lives on instinct, so it doesn't really possess knowledge; Sidney didn't know any of the characters before the story began; and the priest had met Julian before, but didn't really know him personally.

Comic!

This is a complicated question, actually. The person that the female MC THINKS is the Big Bad, she DEFINITELY knows, to the point that she spends decades hunting him down. The person she thinks is the Big Bad definitely recognizes her as a thorn in his side, but to him, she's a medium-sized annoyance, whereas for her, vengeance against him is one of her main motives. (Turns out, he isn't even close to the Biggest, Baddest thing that happens to her. He's just the catalyst that starts her journey.)

None of this has happened in the actual comic thus far, as I'm only on page 5 (of 7) of the prologue... but it will!

One of the main characters has encountered the villain, the other only knows about his infamy.

Ronan knows the big bad from his time in the military. I can't say anything else about anything without spoiling everything.

Hmm there's no real big bad in my current novel. Even the MC, Sandra, isn't exactly a good person.
Since it's a murder mystery, I can't really spoil but Sandra knows the "bad" person - although obviously, she doesn't realize he's bad.

In Shackles, the bad person is more obvious. The Empress Dowager is the MC and needs to escape her devious prime minister's plot.

Since Dark Bytes is an anthology, it's harder to pinpoint the bad person specifically. In general, the big bad is humanity or rather, how humanity creates and uses advances in technology.

Yes, my MC knows the antagonist. He was basically forced into joining said antagonist's cult/organization at a young age and is at the start of the story out of their reach for the first time, which leads to a lot of learning and healing on my MCs part. As for what happens between them after that... Well, we haven't gotten to that yet

My MC knows the big bad, because the big bad was her stepmother. She was incredibly cruel to my MC.

It is a bit early to reveal the "big bad" of everything, but Fang does already know his eventual enemy.

My MC doesn't know who the big bad is. But he'll find out eventually

My MC does know who the Big Bad is. He's her dad!

My MC knows him quite well but doesn't know that hes is evil and therefore can't really comprehend their power.

The big bad guy isn't one specific person, but MC does (or will soon know at least) the big bad's hench-woman

My MC doesnt know the big bad yet, but it'll be fun figuring out how they'll get to meet each other for the first time

Without spoiling too much, I will say the MCs of my comic know the big bad a little bit.
At this point however, they haven't even shown up.

For Clara, she initially didn't know who the true big bad was, but as she digs through her mother's cold case, she ends up discovering much more than she bargained for. Currently, she does know who that villain is, but she's taking her time for her sweet revenge

(And yes, there's a ton of drama in my novel )

My MC does in fact know my big bad (of which there are a few). HOW she knows them is actually something I don't want to spoil just yet, but it's a person somewhat close to her she doesn't suspect.

Technically, my MC has met the big bad, but she doesn't know them...the how of that is a huge spoiler though so I can't say much about it

In Izzy!; the current, ongoing story arc entitled "The Power Of Friendship" has introduced other kinds of gnomes who mainly focuses on adventures and heroism. Izzy is not aware of the looming threat of the series's current villain a.k.a. the Dark One. However, being curious and friendly that he is, despite not having the proper training nor experience to handle such a dangerous task, Izzy had his fate intertwined with a party of gnomes who already knew each other before the quest began. And so... the story unfolds...

Ooof in my comic the big bad is such a big spoiler I don't wanna reveal anything about him at all. XD All I can say is that yes, he does know the main protag. There are a few minor villains too, the MC isn't a big fan of them. XD

For my Star Wars comic, KIRA: A Star Wars Story, the main character, Kira does know the villain. The villain, Zur'por was the Padwan learner of Jedi Master Kazu Tyrbus. As a baby Kira was adopted by Master Tybus, but Zur'por believed this goes against the Jedi code because Kira real father was a Sith Lord. Zur'por and other Jedi left the Jedi Order to form the Order of Purifiers, to remove any Jedi they deem not fit to be a Jedi.

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For my comic Geeking Around: The Webcomic, there isn't really a villain. The webcomic is just based my podcast Geeking Around: The Podcast, featuring myself and cohost/friend Gabby as anime characters. If I had to choose a villain for GA it would be fake fans. As a kid I was bullied a lot for liking comics, video games, anime, Star Wars, etc. While went to the premieres of The Avengers and Star Wars: The Force Awaken, who did I see? The exact same people who used to bullied me for liking it, now claiming they have always be fans.

In my story there isn't a "big bad" but more of like... internal things, such as past experiences, insecurities, and several of other things. My Main Characters, one to be specific, is very marked over his own childhood and the way his parents rised him and that can be reflected on both his behaviour and how he deals with the baby that magically appeared in front of him.

So here it is "We bumped into each other and had a baby", a heartwarming story focused on Co-Parenting.

Bit of a spoiler, but as far as my MCs know right now the big bad is a myth.

Well, Nadhine feels like she knows her big bad, but she might not know him at all. She believes it's the Sultan Kaspar, because of all he did to her parents and to her people. However, she may soon find out her big bad is someone much closer to home...

Iris still hasn't got to the point of having a face-off with the big bad or any petty bads. Although she knows who will eventually be on the opposite of the ring when the time comes. She's a royal, she knows she and her siblings will one day fight for the throne.

Alfredo already faced (Or rather, had a glimpse) his Big bad the day he was separated by his mother... and that is not only the ruler of the empire... but his mother's twin brother... someone very dedicated in keeping an "Order", to which Alfredo appears to be a threat to.

GENRE: Fantasy, Sci-fi Drama
From the nights He used to spend by reading tales of "the Dreamers", the young Alfredo Ananda Kasem always longed to be one of them as well, unaware of the Potential that resides in his Echo, that could change the lives of those around him, whose Stories, connected to His, are the KEY to bring changes to the World of Gaia, and lead to its peace once and for all.

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https://www.instagram.com/fedriz_marini/

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(Trying to be as non-spoilery as possible)
Technically, I would say I have a two big bads -- a "Villain" and an "Antagonist" -- and each of them has a different major conflict. That probably sounds complicated but I can explain. The "Villain" has a grudge against the MC and that led them to send an assassin after him before the beginning of the story and again when they find out the MC is still alive. Meanwhile the "Antagonist" has less of an "I hate you, you hate me so let's fight" scenario and they're just the leader of a country that's at war with the country the MC is in. To actually answer the question, yeah, the MC knows both of them but I can't say how because their identities are hush hush.