I liked Prometheus on Arrow. Most of his screentime is being a smug bastard mocking everybody around him, trying to psychologically break Green Arrow and killing people
He does have his excuses, but at the very least it's very clear they're less "this villain has a point" variety and more of "this guy is fucking mental".
>"you can't use your father's memory to justify a killing spree"
>murders dozens of innocents who had nothing to do with his father pretty much to fuck with Green Arrow who did kill his father
>kills his own wife and then has the gall to blame Green Arrow for it and seemingly actually believe in it
>when he loses, commits suicide killing his own loyal followers via dead man switch explosives just because he was hoping Green Arrow's allies would die as well
>the father he's supposedly avenging wanted to disown him because even he thought his son was fucking insane