It was difficult to finish:
The Legends started out really well up until about episode 30. Up until episode 30, the drama had a really good synopsis, it was interesting, unique and had great potential. However, from episode 30 onwards it was a let down. I found it really hard to not skip sections within each episode and found it difficult to finish in general. In saying that, it was not that bad, just not what i expected to happen.
In my opinion, the drama became a drag because various ideas in the drama were reused (can't explain in detail otherwise the drama will be spoiled) or the flow was just really slow with no action happening in certain episodes.

Confusing scenes:
Towards the end of the drama it was quite confusing. I believe it was due to how the parts in the episodes got put together. Even after finishing the drama I have no idea what some of the certain scenes meant.

Ending:
The ending of the drama, I did not enjoy at all. It felt really rushed but at the same time dragged out. I think they could have just stuck to one impactful ending scene. The part with the kids was really confusing and weird too.

Nonetheless, the casts acted really well and really portrayed their characters and emotions really well and the actors had great chemistry. I would recommend this drama for the acting and if you just want to watch something on the side but don't hold great expectations.