So, I was watching Single Dad in Love and was wondering if anyone knows of other rom's where the male lead is referred to the same way *Ahjussi*  or were maybe in a similar sort of situation.   Any genre/setting is fine, but I would really prefer the male lead not be some douche bag,  I like male leads who are, at least relatively, decent people, I don't mind them being 'bad', like a pickpocket, or something like that, but I don't like them being mean or like that.  

Edit:   Also, like romances with the 'fall from grace' sort of setting, where one of the leads was rich/high status, and for some reason or another, end up losing their wealth or status  With this one, it can be either of the leads that loses their position, I don't mind revenge stories, but I don't like when the 'revenge' has to do with like, the person getting with someone to steal all their stuff or something.  If there's a relationship, I want it to be a relationship, not just some 'I wanted to ruin you so I got with you' bs

Thank you for any time spent reading this
I haven't watched Single Dad in Love, so I may not know exactly what attracted you. However, your description of your preferred male lead seems to fit perfectly w/ :
Lee Dong Chul (played by Song Seing-Heon) in East of Eden

The lead girl calls him Ahjussi throughout the drama.
A soft-spoken good-guy w/ a tough bad-guy image.
He is a very decent, kind, selfless, mature, patient, reasonable, brave, intelligent hunk of a man.  
His fall from grace is the tragedy that befalls his family and forces him to change course, from being a scholar and studying to be a prosecutor, into getting involved with corrupt rich businessmen and gangs.
Drops out of school, but continues to educate himself. He dedicates his life to his family and loved ones, and makes huge sacrifices.
His aim is to get revenge on the murderer of his father ... he never ever uses the girl, his boss' daughter. In fact, it is his boss who forbids them from getting involved.

Single Dad in Love looks like a light Romantic-comedy ... East of Eden is a serious, melodrama. It seamlessly interweaves  family dynamics, business, politics, history, tragedy, revenge, bromance and true love romance.
@rainruma  that sounds spot on, definitely looks interesting and I will check it out, the series dont necessarily need to have both the separate criteria, but its ok if they do.   And yeah,  Single Dad in Love was, for the most part, a bit more on the light-hearted kind of side, but that's ok with it not being like that.  Thank you for the rec
Golden Bride- the female lead calls the male lead Ahjussi throughout the drama. The male lead was the top of his class, looking like he was going to be extremely successful, but he developed a panic disorder and couldn't get out of his house. Not exactly the fall from grace, but it kinda fits.
@squeakyelle  I agree, I think that scenario fits in with the kind of 'fall from grace' scenario also, it sounds pretty interesting, don't see very many Vietnamese characters (even if played by Koreans) in the shows, so I look forward to it, plus, Lee Yeong Ah is probably one of my favorite actors, I usually like the way she pulls her roles off.   Thank you for the recommendation
Lol, you are describing Ojakgyo Brothers, it sounds like.  Try that one, if you're not afraid of a 58-ep family drama.  The one/main brother's storyline has the lead girl calling him ajusshi, and she's got the "fall from grace" thing going on too.

That drama was such crack to me when it was airing :)  Bit of a slow start, but then it gets really good.
@zeamays  It seems interesting, it sounds like they're trying to put a lot of main characters and stories into it, but I'll give it a try, thank you for the rec
So Ji Sub does a lot of these. and he does them very very well. 
I'm sorry I love you, it's a sad story but I highly recommend it. The main female lead calls him Ahjussi through out all the drama.

Delightful girl Choon Hyang, here it's not the main lead who is called Ahjussi but the second lead. I really like this dramas, and have watched it twice.