The Warden of The Witches - Chapter 6:

In the book, the supporting male lead is the older brother of the female lead. The supporting lead has a cold and desolate personality and is despised by the female lead due to his terminal illness. However, when the female lead acted viciously and was abandoned by everyone, he still protected her, sacrificing everything for her and even dying for her.Su Ci has transmigrated into the book, becoming a little rabbit raised by the supporting male lead, and she has discovered that her life is tied together with this terminally ill supporting male lead.After becoming a little rabbit, Su Ci can only sleep on the supporting male lead’s dusty bed every day, eat withered carrots, and guard against the female lead, who occasionally tries to pluck her rabbit fur. To turn back into a human, she needs to find ways to get close to him every day.The supporting male lead noticed that lately, his pet rabbit always wanted to kiss him. Until one night, he leaned down and kissed this soft little creature, and it unexpectedly transformed into a beautiful little fairy!…The female lead encountered trouble, so she went to look for the supporting male lead, whom she always looked down upon. Unexpectedly, the young man, who was previously poor, down on his luck, and nearing death, had become a scion of a wealthy family in a blink of an eye, and by his side was a girl as beautiful as a fairy.But what made her jealous was that the always-cold and aloof supporting male lead actually kissed that girl gently in front of everyone!

Su Yao passed through and traveled to the Marvel world to become a mutant. He was still in the experimental base. He expressed a little panic…

Fortunately, at the critical moment, the mutant ability ‘imitation’ was awakened to imitate the opponent’s ability!
…
Imitation object→Orochi (title: Sun God, Will of the Earth)
Imitation object→Wanda (title: Scarlet Witch, owner of chaos magic)
Imitation object → Sun God…
…
Professor X: “We must find him as soon as possible and guide him to control his power to avoid causing irreparable disasters!”
Magneto: “You are my child???”
Thor: “Brother?”
Loki: “?”

- Description from novelbuddy

After discovering about her wealthy husband’s affair, she humiliates the adulterous pair on the streets and divorces him the very next morning. Just as everyone anticipates her downfall, she goes on to marry the most brilliant bachelor in the nation whom her unfaithful former husband cannot hold a candle to!

The story is about a a hitman, Who dies because of his own recklessness and transmigrates into a game he used to play after his retirement as a hitman.I'm not gonna spoil any further, but i might answer few of your questions.Is MC overpowered?Nope, he'll become strong over time and all battle he'll fight will be because of his effort and techniques.Is there magic and adventure?Yes! It have both magic like normal isekai with adventure and fighting with monsters and many other things. There are other important things like “Essence Stone” But let's talk about it in the chapters.There will be harem?Not really, He will be in contact with many beautiful female and males but one waifu but i haven't decided yet.All i can say is, give it a try, I'll try my best to make it worth your time.