Idea 2

For this mc get reincarnated again as anobody in middle class family in mcu without any wish but slightly higher Intelligence and better Memory.

In this mc have a pet (author can decide the pet it may b cat or dog or any common pet) in the family. When mc realize he didn't get any powers he decided to build himself better in physique so he can atleast tackle small villains which can harm him or his family. He goes for in the field of medicine to cure his grandma or grandpa (author can decide) from a disease which doctors don't have a cure and have only few years remaining for the grandparent when he is of age to choose the subject for further studies.

As he is above normal in memory he is easily able to done his studies in medicine and goes to find a cure... which he is able to find and cure his gandpa/grandma. But now his pet dies due again a mysterious disease. Mc is in emotional turmoil due yo this and dedicate his next study on animal. As he has to diverge his whole study now it takes some time but he is able to do it. As there weren't many researcherrors for medicines for animals he started doing many research for disease of animals. During one such research, an experiment goes wrong due to his mixed knowledge of human and animals botany, an error if u want to say.

After this mc gets the power to turn into animals and insects (Just like banner get power to turn into hulk but more controlled). This power starts with to turn in only to those animals with whom mc spends time and have feelings of love and care. The first animal he is able to turn into is like his old pet.

As mc get more control over his power he is able to turn into other animals, follwed by insects. Later on he is able to change the size of animals or insects which he turn into like dog sized rat or ant size dog. Author can use the animals and their size according to the need of story.

Lastly when he is able to get full control and get blessing from Odin he is able to transform even into mythical creatures like Dragons.

I don't know if marvel has any character with same power as i gave to mc because i have only watched MCU and haven't read Marvel comics so i hope this is original. The timeline can be adjusted like MC gets the powers a year before the event of Iron Man 1 or during the same time when Dr. Banner met with accident and becomes Hulk.

Again any1 interested in writing a story using this idea is welcome to write just leave the link to story in inbox or at least in comments section.