Queen of the Game (2006)

both dramas involve revenge, losing memory in a tunnel, and melo things!

In both dramas the lead male approach the lead female in order to seek revenge from their fathers: revenge leads to love.

The main guys in both hate the female leads at first due to their family's past but end up falling madly in love with them in the end. Also these two dramas are probably the most romantic one's I've ever seen with enough angst to tug at your heartstrings.

A man takes revenge on his father's death by making the enemy's daughter fall in love with him and then treating her badly.

Both dramas have revenge plot story where ML plan to get revenge and use the FL as his revenge tools. But the ML has different reason to get revenge. Both of dramas have same story trope where ML lost and got memory lost because of accident. Both of FL fallen pregnant and kept the pregnancy after the ML's lost accident. The FL and ML met again after 5 years with the existent of their son. Both dramas have strong ML's character.

The male leads in both use the female leads who happen to be heiresses for their revenge by making them fall in love with them.

Both guys end up losing thier memory. Also, both female leads end up having a child by the main guy and keeping it from them.

The dads in both cause one of the main character's parent to die. After falling in love the main couple must over come this conflict and parent obejections in order to have their happy ending.