Question

خیلی نامردی به انگلیسی چی میشه؟

Answer 1

I think it's context specific and there's not an accurate word for that in English but here's some suggestions:

You sack of sh*t

http://www.urbandictionary.com/define.php?term=sack%20of%20shit

You devious bastard

You asshole

Answer 2

Namard is a person who isn't honest,and does not act according to his commitments and promises

Namard=ungentlemanly/dastardly/unmanly/cowardly/impotent/poltroon/craven

In India, the word na-mard is used to mean 'impotent'. It is also used to mean 'Coward', 'Worthless', 'Fool', 'Inefficient', 'Incapable', 'Unworthy' etc but this word is only applicable to men.

The word namard is used in India meaning unmanly,impotent

 

نامرد. [ م َ ] (ص مرکب ) بی مروت . (آنندراج ) (فرهنگ نظام ). || ناکس . بی غیرت . (ناظم الاطباء). بی حمیت . بی عار و ننگ . بی تعصب . بی رگ . بی درد. بی عار. که مردانگی وشجاعت و دلیری ندارد. دشنام گونه ای است 

You arrant coward/You poltroon