A couple of rules:
You can't have more than one character from a franchise.
The character can't be omnipotent
You won't gain the downsides of their powers
You can not leave the fictional world you chose
Here is my example:
For my fictional world I'd choose League of Legends
My characters:
1) Doctor Strangefate (Marvel + DC)
2) Mitsuba Higashikata (JJBA)
3) The Hanged King (SCP Foundation)
4) Aurelion Sol (League of Legends)
5) The Father (Star Wars)