noun: poison dwarf, spiteful person
This (pejorative) colloquialism is used to describe an obnoxious person who may attempt to compensate for being physically small through malice and spite. They are regarded as being loudmouthed, impolite, and irritable.
Ich weiß, dass ich manchmal so ein Giftzwerg bin! = I can be such a poison dwarf sometimes!
A man looking enraged. Photo: Andrea Piacquadio via Pexels