I just finished the dramas Cruel Romance and the Lady and the Liar AND I LOVE THEM BOTH SO MUCH! I am trying to find other dramas like these where it has all the jealousy aspects, controlling power man, and love triangles. I am mostly looking for the same time period as these two or in periodic, historical, time periods. Modern Korean dramas are fine too. Thank you everyone! =)

The Disguiser is the only other one I know of like that.
I'm keeping an eye on this topic, I love those drama's. 
Just finished Go Princess Go and has jealousy in it although it's not forceful. Its a drama to take with a pinch of salt as it's totally hilarious but it's a good watch.

After i saw CR and L&L i watched too late to say i love you. Fits the description and it's within the time period you want.
Sound of the Desert ....has a strong love triangle.... Main lead is very jealous, but he's also very patient and supportive.... It has a lot of the angsty jealousy you want, especially later on!
Love H20 has a love triangle. The only difference in LoveH20 is that it revovles around a video game, rich guy vs. rich guy fighting for a pretty girl, and a LOT of cheesy scenes.