Why did it take me to post this?
You guys have forgotten your childhoods. (Also, while I'm on the subject of Mermaidman and Barnacle Boy: Every Villain Is Lemons)
Now then. Concerning Edgar, he's not necessarily an evil character; in fact, his moral compass tends to point towards a neutral good. The problem he has is that he ends up associated with people who are not so good-natured. Delial Grimsong is a perfect example.Â
Edgar tends to see the good in people that most others cannot, and this lands him in a lot of trouble, because more often than not, that sliver of goodness pales in comparison to the magnitude of the person's natural tendency to do bad things, something he tends to gloss over because "hey, they have some redeeming value." Maybe Edgar just hopes that by revealing and focusing on this hidden good nature, this will somehow cause the person to perform a face-heel turn towards the light, but in cases such as Delial's, the results have been relatively mixed.
Suffice to say, failure in such endeavors often causes Ed a lot of depression.