Thought i'd make a post where we'd post a list of OP seeds, Over powered is when you can beat mom's heart in less than 30 seconds, the format would be like this:
Seed:
Best Character for the seed:
The Items:
Example
Seed: 0BBJ ZEN1
Best Character for the seed: Azazel
The Items: Polyphemus, Ludovico technique, Spoon bender, The Pact, Prayer Card, Experimental treatment.
Edit: Oh and about the seed unlocks, endings 14, 15 and 16 will unlock in seeds.