@Riot: How dangerous is Veigar really?

Basically what it says in the title. Veigar in game is the burst mage of burst mages, sure. But his lore hasn't been updated in quite some time. I'm wondering how he would hold up in Valoran now.

He's completely insane, sure, and it's hard to take him seriously what with the squeaky voice and tiny stature. But he also seems capable of twisting the fabric of the universe to his whims without a second thought. How does he measure up to Syndra, for example? In a lot of ways, they're quite similar-both dark mages of apparently supreme power. Syndra is outright stated to have almost limitless potential, but Veigar LITERALLY has limitless potential-at least, in game. Where does all this leave the yordle megalomaniac?