Yeah, I'll fall on my sword and agree about Overlord. When I first read this guy in LSotW, I thought, "man! what an evil bastard! He's just a psychopath who wants to hurt people just for the sake of hurting people (and proving he's just stronger than everyone else)." I didn't think much about whether he's lawful or chaotic. Now that I think of it, that IS Chaotic Evil.
I don't know whether IDW Prowl is Lawful Evil. He's definitely Lawful, but I don't think he'd deliberately Kill or cause harm just to please himself. To him, causing pain and misery is just a means to an important end.
I do agree about Thundercracker being True Neutral. I wanted to put him on the chart, but I thought Wreck-Gar is more interesting, especially since we're (or at least I am) so use to seeing him as a 'good' character. In his recent appearance in the IDW comics, he was an antagonist, but to me, it seemed like his actions were motivated by mistrust and xenophobia more than anything else. Also, Rum-maj had a pretty tight leash on him, and even she didn't seem 100% Chaotic Evil. She seemed to be motivated by jealously and revenge. Come to think of it, the Junkions didn't strike me as evil, they just felt like they'd been short-changed and were looking to bust some heads to get what they felt was owed to them. They did however enslave to poor POOR sharkticons, so they're definitely not good.