A Champion I have new respect for after Morde's VGU?
Veigar.
Now hold on don't laugh! Hear me out!
Veigar's latest lore update says that he was captured, isolated, and tortured. By who? By Mordekaiser. And not the old "I like my music" Mordekaiser, either; the new "I am going to make my own afterlife in which I reign supreme and control both realms" big bad that has even people like LeBlanc shaking in their boots. THAT Mordekaiser tortured Veigar for his own amusement, intentionally keeping the Yordle alone and isolated. And we've got a good idea what that tends to do to Yordles in the form of Kled.
And yet all in all, how did Veigar come out of it? Well for one he came out of it alive and not as mortar for Mordekaiser's kingdom. So y'know, good start. But even if he isn't all there anymore he definitely came out of it better than Kled's own- self-imposed and without being tortured, mind you- isolation. He's not completely insane, and while he puts forth the conscious effort of being a terrible and twisted villain, in reality he ends up doing a lot of good.
Given what Veigar has been put through and what his magic is capable of, I have new respect for the "Master of Evil" for coming out of it as intact as he did. I'm grateful too- a truly malicious and entirely competent Veigar would probably be one of the biggest immediate threats to all of Runeterra.