Crackgakker

Someone who is delusional, paranoid and generally angry. Normally send shivers down people's spines when he/she/they are nearby. Similar behaviors include being abrupt, loud, and terrifying. Bonus points if the person is german.

Student 1: That teacher was really angry! She told someone off for talking in class when he didn't say anything!
Student 2: Yeah she's a real Crackgakker