Sorry for the fans, I finished this because the reviews were so great, but it felt like forever to go through only 12 Ep, and I still do not get the enthousiasm...
From my point of view, every character is one dimension, their relationship not even remotely believable, the scenario and dialogues are almost always so un-interesting that they have to go for the most over-the-top twist to hide that their storyline is actually quite thin with tons of plot holes...
If you are interested in revenge or time-travel stories, there are certainly much better dramas available... All in all, drama is a good candidate for the worst drama I have ever seen.