Izuku Midoriya and Tenko Shimura. Two sides of the same coin. Two children who at one point, aspired to become heroes. But only one got to go down this path. Tenko became a villain, while Izuku became a hero. But what if, by some ripple in the cosmic universe, these two changed their positions. What if by some sheer, chance, these two became the polar opposite of themselves. This is... what if Izuku and Tenko, swapped fates.

The superhuman society is great for some with popular quirks but not for quirkless let alone people whose quirks are seen as villainous, and that is how villains are created. (Villain Izuku, Izuku Shigaraki Dad All For One)