Atyachaar is a Hindi word made up of two words ati and aachar. Ati means a lot, or too much, while aachar means behaviour. Hence, the very literal meaning of the word Atyachaar is extreme behaviour.
However, in popular language, atyachaar is used to describe oppression, or even closer, brutality.
Thus, the phrase Emotional Atyachar means brutality done with emotions as the means, that is, emotional blackmail.