Zim is, an Irken with megalomaniacal, sadistic, sociopathic and narcissistic tendencies. He usually ends up being a danger to himself and his own people.
He often acts like a spoiled brat, and is far too stupid and incompetent to actually do any proper harm. He is VERY hard at hearing. He’s very stupid and loud and annoying but very persistent. 

Zim is viewed as a villain in some cases but is also considered an anti-hero. He’s always screaming and whining, and hates Dib.