Over a barrel
指一个人出于某种无奈，只能听凭别人摆布，别人让他怎么干他就得怎么干
John had Bob over a barrel because the latter owed him money
鲍勃什么都得听约翰的，因为他欠约翰的钱。
During the negotiations the opposing faction had us over a barrel.
在谈判中，那个对抗的派别使我们一筹莫展

over one's dead body
是想方设法阻止某一计划的实现。
You can have this over my dead body.
除非我死，不然你休想得到这东西。