这几个词语都有“终于”或“最后”的意思.
1、at last 强调久等之后.比如:
（1）When the fire had at last been put out, the forest authorities ordered several tons of special type of grass seed which would grow quickly.
在火终于被扑灭的时候,森林管理局订购了好几吨特殊速生草籽.
（2）When the dentist at last removed the cotton wool from my mouth, I was able to tell him that he had pulled out the wrong tooth.
在牙科医生终于把药棉从我嘴中取出时,我才勉强地告诉他说,他把牙拔错了.
（3）At last firemen have put out a big forest fire in California.
消防队员终于扑灭了加利福尼亚州的一场森林大火.
（4）At last, the nurse appeared at the door looking very tired.
终于奶妈带着一副似乎极为疲倦的模样出现在门口.
（5）At last, they got to the restaurant.
最后,他们到了那家餐馆.
2、in time 表示经过一段不定的时间之后,比如:
（1）In time, all Sams money was paid back in this way.
山姆所有的钱终于都用这种办法归还了.
（2）You will learn how to do it in time.
这项工作你最终总能学会做的.
注:in time 还有“及时”的意思.比如：
He got home in time for the world news on TV.
他回家正好赶上看电视台的国际新闻.
3、finally 也表示久等之后,但有时表示在一系列因素的最后一个之后.例:
（1）After putting it off three times, we finally managed to have a holiday in Greece.
推迟了三次度假之后,我们终于在希腊度了假.
（2）He finally agreed to my plan.
最后他同意了我的计划.
（3）However, he reached the shore finally.
最后他还是游到了岸边.
4、in the end 和 finally 同义,但 finally 一般位于谓语前.这些词除 finally 之外,其他三个都可以用在谓语前,也可位于谓语后.例:
（1）In the end, we stay at home and look after everything.
最后,我们还是呆在家里照看着一切.
（2）He tried many ways of earning, in the end he became a farm labourer.
他试过许多谋生之道,最后他做了农场工人.
（3）His efforts were well paid in the end.
他的努力终于得到了很好的结果.
（4）In the end they reached a place of safety.
他们终于到达了一个安全的地方.
祝你学习进步,更上一层楼!请记得采纳,谢谢!(*^__^*)