Idea 2

1.Mc Is Reincarnated or transmigratedg

2. Mc is sent to akame ga kill with the powers of the adaptdoid from marvel

And his goal is gain all the powers of the teigu.

3. MC is reincarnated as akame and kuromes older brother and along with become an assassin hes and alchemist.

Routes 1 joining nightraid

Route 2 pissed off that akame would rather pick a bunch of strangers over her own siblings he vows to kill not only night raid but also August and the emperor all the while looking after kurome.

Route 3  he takes akame and kurome and runs away with the help of a gamer system(incest if you like)