Both are fantasy kdramas
Both evoke deep and intense emotions
The leads in both dramas go through a lot of struggles and challenges to be with each other.
Both dramas have elements of dark magic, ghosts, demons, dark secrets and love.

The female leads in both dramas are from rich and well-known families.
In both dramas, the female leads are going through a tough moment connected to family. One is struggling to pay off her late father's debt while the other still performs daughter-in-law duties to her ex-husband's family for the sake of her own family.
For the female leads in both dramas, the presence of the male leads is like a breath of fresh air amidst their problems.
The male leads in both dramas are witty, sweet, kind, funny and offer great comfort and support to the female leads.

Both are fantasy dramas in which the male leads are powerful beings.
In both dramas, the main leads are destined to be together.
In both dramas, the male leads protect the females with their power.
There's also a fierce battle between evil and good powerful beings (male leads) in both dramas.
Both dramas have elements of fantasy, rom-com, sageuk and thriller.

Both dramas talk about everything related to fashion, luxury and influencing.
Both dramas capture the highs and lows of the fashion industry as well as the role of certain key players in fashion.
The only difference is that the fabulous revolves around four friends trying to make it in the fashion world whereas celebrity revolves around the lives of influencers who'd do anything to be known.

In both dramas, the female lead gets married as she sees that as the only way to get back at those who hurt her.
In both dramas, feelings of love and romance begins after marriage.
The only difference is that in vengeance of the bride, the female lead married into the family she wanted to take revenge on but with perfect marriage revenge, the female leads gets married into a powerful family as revenge against those who raised her but never made her feel loved.

Both dramas have strong male leads whose first impression comes off as being arrogant.
Both dramas have male leads who are demons and possess powers they use to protect the female lead from hurtful or painful experiences or people who wish to hurt them.

Both are office romance dramas specifically one between a boss and his secretary.
Both dramas have male leads who are a bit self-centered but very sweet.
In both dramas, the male and female leads in an attempt to overcome their differences and get along well, develop romantic feelings of each other.

Both dramas are office romance
Both are noona romance dramas
In both dramas, the female leads dated someone in the same office space before liking the male leads.
Female leads heal from broken heart in both dramas.

Both dramas center around rich and powerful families
Both dramas tackle marital issues such as infidelity
In both dramas, the female leads take revenge on their husbands for having extra marital affairs and deal with the mistresses.

Both dramas have great female cast
Both dramas revolve around powerful, rich, intelligent and smart women who are affiliated to powerful families and live a life of luxury.
In both dramas, these women strive to achieve and protect what they want (freedom, peace of mind, happy marriage, affluence, power etc) and most of all take revenge on those who hurt them.

Both are traditional dramas set in the joseon era and they portray how life in the palace is from ; life of a crown prince, palace politics, power trip in the palace etc. They both capture interesting traditional royal life.

Just like may I help you entails performing most wanted desire of dead people, the deliveryman passes on information from the dead to their loved ones.