in the end~In the end,he killed himself.in the end =finally, at last.最后他还是自杀了
at the end of~At the end of this street a body lay there.街尾躺着一具尸体
by the end of ~by the end of this year,they will have finished work on the new stadium(在今年年底工人们很把路铺好）注：have+过去分词表将来完成时
by表：在某时之前,并不晚于某时的任何时间.只能与时间点的名词或词组连用.在肯定与否定句中有区别
i will have left by monday到星期一我将离开（星期一之前的任何时间）