忘恩负义

wàng'ēn-fùyì

[forgetful; turn on one's friend; kick away the ladder; be devoid of all gratitude] 忘却别人对自己的好处, 做事有损于过去的恩义

如此忘恩负义, 以致弄到牺牲盟国去订"密约"的地步