HiTherefic
I suggest a fanfic about the Grimm series, the character would be reincarnated in the body of a young grimm who was trained by his family to be a hunter since he was little, but everyone dies in an ambush of the black claw along with the royal families because they were afraid of his family , who used knowledge about the wesen to become stronger and created weapons and armor using the wesen they hunted and killed, he would join Nick after he became a grimm and his romance would be with Trubel the other grimm
how about if you have the mc start in one of the Spiderman movies as peter parker but here is the twist this verse of peter parker has got the x-gene and the power he has is ultimate genetic adaptability which means he can gain powers from any dna/venom that which is injected into him also it allows for him to gain the best traits/powers from the dna he is injected with but he won't know about this in the beginning and i think that if you want to move the Mc to the dc verse you could use the Spiderman into the spider verse movie as a jumping point to move the Mc to the dc verse through a multiversesal/omniversesal glitch that happens when the machine is turned onthis is just a thought I had. Plus, you could make it so that when it happens, he gains access to a jumpchain document for the dc verse so you could set up his background that way and give him powers that way because the glitch also reset his x-gene thus causing him to lose some of his powers that he has gained or all the powers he had gained but it did give him the gamer ability inventory so he can store what he wants away