This is actually a 2-part convoluted request:

#1. You know how most dramas have that male lead that is a jerk/mean/arrogant/bad boy on the outside but misunderstood/nice on the inside? Well, I'm looking for the opposite: a male lead that is nice on the outside or everyone thinks he is a "nice guy." Maybe he is nice but hiding his dark side or gets fed up?

#2.  The female lead is the first/only person to realize #1? So NOT something where the male lead is really nice, everyone figures out he's out for revenge but she is the last to know.  

Honestly, I feel like dramas like #1 are hard to find as it is, so #2 is more of a "if possible" request. The only example I can think of is Cheese in the Trap. 

Because of the male lead's dubious nature, I don't need the leads to end up together, but I do want him to be the "male lead"--as in, FL does not end up with anyone else. Any genre/country.

Thank you!!

Your request makes me think of You Always Inhabit My Heart.

There are two male leads in this series, one of which is a total jerk to the female lead. (From what I've seen, he's got no redeemable qualities - though I haven't seen the full show, so who knows). Anyway, this jerk and the female lead used to go out, but she's moved on with her life... until he ends up working in the same company as her, allowing him to once again torment her in secret.  She knows he's a jerk from their previous relationship (and his current torments), but he appears as an upstanding nice guy to everyone around her - though people are starting to figure him out later on.

The second male lead is the "nice guy" in the triangle whom the female lead wants to start a relationship with, but her feelings for the jerk makes her waver between the two, and their history keeps getting in the way of this new relationship she's desperately trying to start (plus she's a bit spastic around guys, so there's that).  Anyway, it looks like they are trying to get a love triangle going, because the female lead is very conflicted about her feelings for the jerk knowing he's no good, but remembering the good times, and also the bad times.

But yea, I haven't seen the full series because it's slow getting subbed, so I may be off base here. But it's definitely got a male lead who's a jerk to the female lead and the people surrounding her don't notice (for a while anyway), because he only shows his true colours when him and the female lead are alone.

Thank you @Chomelea! 

I'll try to give it a shot but to be honest, the lack of subs is a bit deterring. And the fact that the comments section is all about how the FL is a complete idiot =(. To be honest, I requested something like this to indirectly look for a smarter, more perspective female lead. Like, here's this charming male lead that everyone thinks is a (harmless) nice guy and the female lead can see that there is something off. Basically, exactly like Cheese the the Trap lol.  My other inspiration was from the Taiwanese drama Devil Beside You. There's a scene where the golden boy 2nd lead the female lead crushes on at first kind of snaps and says something like, "just because you think I'm nice, does that mean I always have to be nice?" and that just hooked me right there. Plus, the cold tsundre male lead thing can get stale.  

Yes, I watched Devil Beside You a while back and remember liking it - the male lead was more of a teasing tormentor in a charming way if I remember correctly, but when it comes to You Always Inhabit My Heart, so far, no such luck when it comes to the jerk - he's just a complete jerk with zero charm.  If what you are looking for is a charming jerk, you're not going to find it here. He's the least charming character imaginable and if she ends up with him, I'm literally going to scream at her through my monitor.

As for the female lead, I get how they are trying to show how broken she became after her relationship with the jerk, but it's hard to watch her act the way she does. If she acted stronger, I don't think the jerk would bother with her anymore. I would love to see some progression in that the female lead doesn't act like either a spaz or a doormat all the time, but from what I've seen so far, I'm not going to hold my breath on that one. I did try finding the manga it was based on to see if it got any better, but I couldn't find it online.

Anyway, wish I had a better suggestion for you, but yea, the category I think is very limited lol... Figured it might be worth a shot since it reminded me of some of your criteria.

I will have to watch Cheese in the Trap at some point, though. Sounds like it would be a much more enjoyable show. It's been on my watchlist for a while now, but just haven't gotten there yet :)

Ah,I meant the 2nd male lead in Devil Beside You, not the male lead. I love Ahmon (the male lead) but yeah, I do consider him the classic bad boy-on-the-outside type and he's not what I'm looking for here. That scene I mentioned above was very brief, but it just opened but all these "what if" scenarios in my mind. I think another drama that plays on this idea is Black Devil and White Prince but I haven't watched it yet, so I'm not totally sure. 

The drama you req'd does seem like a good fit tho. Female leads are tricky. While, rationally, I do believe a person should be vulnerable and broken after a traumatic incident in their lives, watching it from the audience POV can be painful. 

But yes, watch Cheese in the Trap. Or better yet, go read the webtoon! It's so unique and well done, it's hard to find anything remotely similar.  I cannot recommend it enough!