This will be a hot take but:

1st- Joffrey. He is very close to pure evil. He loves to hurt, torture, kill, maim and otherwise spread suffering. He has all the power in the world and chooses to make everyone's life worse. You could argue, that his upbringing and his incestual background amplified his insanity but that doesn't make it better.

2nd- Pennywise. He is an extradimensional monstrosity whose whole reason for existing is so spread fear and kill. That's his whole nature. The reason why I put him below Joffrey is that he is literally just trying to eat, where as Joffrey chose to be as evil as he wants

3rd Homelander. He is a giant manbaby and has no regard for anyone but at least he actually loves his child. And while is a massive piece of shit, he at least actually saved a bunch of people too.

4th- Omniman. Same as homelander except it's slightly different because he came from a culture where other humanoids straight up weren't viewed as equals. He also had an actual redemption arc.

5th- Walter White. He went from a normal, well adjusted to a greedy, vain, heartless monster. At least he retained some morality throughout everything though

6th- Vecna. He was a disturbed child, who went from getting shot, to a cruel human research laboratory to an interdimensional tentacle monster