I find Michael Savage the most vile, but I would say Limbaugh is actually the worst. As someone who has actually listened to his show, the quality of his show is actually incredibly low, I don't know how he has so many listeners when he goes on these ramblings of alternate realities that make absolutely no sense. . Sean Hannity is the most annoying, though not the worst. Beck and Levin are tolerable to me but still nutjob insane on many things.
Inspired by my parents who listen to Levin on a nightly basis.
I don't actually know who Levin is so I'll comment on who I do know. I find Hannity to be the worst because he seems like the biggest shill.
Limbaugh and Savage are pretty vile and Beck is in his own league of crazy, but all three strike me as genuinely believing everything that comes out of their mouth. When they say something crazy or stupid, I believe them when they say that's what they believe and that's how they see the world.
Hannity comes off to me as totally phoney, a guy who would say anything if you threw the right amount of money at him. I get the same vibe from Laura Ingraham as well, but Hannity annoys me more.
I'm pretty sure Limbaugh and Savage say a lot of things they don't really believe, but at least they are creative.