Welcome 2 Life

Both have some supernatural twists that deals with "dreams" (or technically, parallel timelines for W2L). Both encountered mysteries that they can solve because they have witnessed/experienced it.

The starting of the drama is very similar as the ML in both dramas start off as a corrupt individual (works for money) and then are forced by circumstances (K in Bad and Crazy, parallel Universe in Welcome 2 Life) to fight against the bad guys who supported them.

And they both get assaulted by the FL in the first episode as soon as they are introduced.

Both male leads are living in a parallel reality, both dramas have violent crimes in common and police investigations.

Similar Supernatural Story. A chance to change for the better for the selfish protagonist.
A bit more character driven to be honest

Both have a main character who goes into an alternate universe where they are married and have children.
Welcome to life is about law while switch is about actors.

They both have a parallel universe in which the main male character can travel to and from under special circumstance.
Both female leads are police officers.

Both drama's have the same central premise of a prosecutor being given a second chance. The second chances are given through fantastical means