Literally, it is someone who has been "raised badly," in other words, someone who is spoiled or ill-mannered.
A malcreant is a term that is derived from merging the words "malicious" and "miscreant". It is used to describe someone who is not only acting in an immoral or unethical manner, but also with a deliberate intention to cause harm or trouble. Essentially, a malcreant is an individual who actively engages in malicious or harmful behavior.