“不负义务的”可以翻译为“derelict of duty” 或者更通俗地说“neglectful of one's obligations” 。
“derelict of duty” 是一个较为正式和书面的表达，强调严重失职、未履行应尽职责；“neglectful of one's obligations” 意思更直白，突出对自身义务的忽视 。例如：
The official was derelict of duty in handling this emergency.（这名官员在处理这起紧急事件时严重失职 。）
He was neglectful of his obligations as a father.（他没有尽到作为父亲的责任 。）