When Arrow debuted in 2012, its fans marvelled (no pun intended) at DC's decision to go dark, gritty, and above all - realistic. That all went out the window with the introduction of The Flash in 2014, when the Arrowverse was born, and with it came metahumans, aliens, time-travel and magic.
Somehow Arrow survived, and both shows continue to thrive, with the Legends of Tomorrow and even Supergirl recently getting in on the action - but you can't have that many superheroes without a few equally supervillains.
For every season of Arrow, Flash and Legends (I'm excluding Supergirl villains on the grounds that she only recently became a part of the Arrowverse), they have faced a new enemy, a 'big bad' if you will - suitably bigger and badder than their predecessors.
But this would be no list at all if I were ranking simply on size and evilness. Instead, the villains are ranked on their respective story arcs; how much impact they have had on our protagonists, and their own backstories and justifications.
Vandal Savage's introduction to the Arrowverse was certainly explosive enough, literally destroying Star City and its inhabitants, before a time-travelling Flash saved the day. But once you look past his first appearances on the CW, you realise that there isn't a whole lot more to Savage than just the fact that he likes to destroy stuff.
Strip away the fact that he killed Hawkman, as well as Rip Hunter's wife and child and supposedly cities full of people in the future. What you have left is an immortal tyrant, with centuries of training in martial arts and magic, who loses more or less every time he enters a fistfight.
Separately facing off against White Canary, Heatwave and the Hawks in the Legends season 1 finale, he is fairly easily beaten in all three, and not at any point does he threaten the Legends physically. His appeal is that he is supposedly one step ahead of them at every turn, but you expect more of a threat from a villain who is a hand-to-hand genius in the comics.