Business Drama~~~!

Golden Empire - corporate espionage, hostile takeovers, greed, corruption, revenge, psychopathy, mental illness ... While all this might sound a bit over the top, trust me it isn't. This is the most intelligently written Asian dramas I've ever seen. Don't expect the usual dumbed down, idiotic K-drama fare where the characters behave without logic and or forethought. Everything about this drama is top notch. The acting is superb, the dialogue is philosophical and deep. The pacing, character development ... all on another level. For some people the male lead is somewhat of an anti-hero. For me, he is a brilliant man despite his faults. The show will have you questioning whatever moral code you subscribe to as you go on this journey with the characters. While I tend to prefer mostly romantic stuff, this is by far the best K-drama I've seen in my 3.5 yrs of watching drama.
 
Hanzawa Noaki - a survival of the fittest type story in the cutthroat, dog-eat-dog world of corporate Japan.

A Clear Midsummer Night - mixture of family drama, romance and corporate scheming. The business aspect takes up a good portion of the drama and affects the family and romantic relations of the characters.

Others that I haven't seen yet, but heard are great:

Roosevelt Game

Punch - written by the same screenwriter as Golden Empire. Like I said Golden Empire is the best written Korean (Asian) drama I've ever seen so this gives me confidence that Punch will live up to its reputation.

falling for innocence

Also five fingers. MC is an illegitimate son if a rich piano maker family. He and 'brother' fight for dads attention leading to a very dark plot. Romance involved, the business side of these expensive pianos involved, MCs are male (and very male at that! Ju ji hoon and ji Chang wook). Lots of evil plotting, revenge, jealousy and just very good acting. It's a slow starting drama with loads of flashback to which I dropped it at first but you realise later how important the flashback are. Stick with it

^
i also confuse hahaha
but based on her summary, i would suggest Mask 

Have you tried Hotel King?

Lovers, Cruel Romance, Lady and the Liar, Falling for Innocence, Misæng etc are misleading recommendations if I understood the OPs request correctly. These are not business dramas. The male leads may be businessmen, but these dramas are romance centered and focused (except Misæng, which is more of a slice of life type drama).

Whilst shows like Golden Empire, Hanzawa Naoki, Roosevelt Game etc are firmly rooted in the politics of the corporate world, often with little or no romance. In GE there were hints of a romance, but it was never explored. Hanzawa's wife was very supportive of him, but there wasn't that many romantic scenes. As a romance fan myself, I thought I would be bored watching a drama purely about corporate scheming, but both these dramas were top of the line and kept me hooked from beginning to end.

Golden Empire started off a little slower than Hanazawa, but around the 8th or 9th episode that's when it became like crack cocaine for me. I couldn't stop watching, it was so interesting. I remember I missed work two days in a row because I stayed up pass my bed time watching this (thankfully I work for myself or I surely would have been fired). On the other hand, Hanazawa was interesting from the start, had a few slow moments in the middle, but picked up again in the last 4 or so episodes. The slow moments never lasted long in either drama so just keep at it.

If you want a good mixture of romance and business, A Clear Midsummer Night is a good choice, but the quality of this drama (in terms of script, acting, pacing etc) is far below Golden Empire & Hanzawa. It's watchable enough though, if only for Hawick Lau (and his lovely wife irl) who is an amazingly charismatic actor.