In the MCU/Marvel with the Omnitrix/Ultimatrix - Chapter 30: Date with the Queen

The Fake Life of a Villainess: Reincarnated as a villainous noblewoman, you become an experience bag for the protagonist on their journey. You are the target of the maid’s revenge, your half-sister takes away everything that belongs to you, and the grand princess who cared for you for many years finally loses hope and abandons you. The Real Life of a Villainess: You clean up the mess left behind by the protagonist when they disappear. And in their place, you teach her that as a maid, she shouldn’t always be thinking about…

A master assassin transmigrates into an interstellar era.

Jian Rushi, born in a rich family, was a college girl. Due to some economic reasons, her family went broke. Her father committed suicide under great pressure, while her mother ran away with someone else, leaving her alone in this world. As she tried to find some comfort from her boyfriend, she found that her boyfriend cheated on her. Feeling devastated, Jian Rushi thought of ending her life. But she wanted to do a crazy thing before that. Suddenly she remembered she was still virgin. So she decided to sleep with a man before she died. She went to a pub one day and saw a pretty man drinking there alone. She mistook him as a money boy and took him home. After they slept, she had no money to pay him. As the compensation, Jian Rushi became the mistress of that man, who turned out to be a golden bachelor. And a series of embarrassing things happened…

- Description from Novelupdates

Katherine Zara, a single middle aged office worker, went about her day as she always had; wake up, go to work, come home and read or play games. However, today would be different. Before she left for work, her ex broke into her apartment and killed her.

When she woke up, she was given many choices. She could pick her new world, pick her starting point, and pick her system among many other things. And so Katherine decided to become a servant to a villainess.

Follow Katherine as she serves her petty, demanding mistress in a world of swords and magic.

Additional: The Female Lead (Katherine) will be submissive to her mistress, but will be cold towards others. I plan on having some action, but mainly this will be a story about Katherine serving her mistress and leveling up her system.