The worst holiday I've ever been had=The worst holiday that I've ever been had
这是一个含有定语从句I've ever been had名词短语,The worst holiday 作had的宾语,遇到这种情况我们通常采用还原法----把提到句子前面的疑问词或名词短语,再放回动词的后面,通过动宾搭配来分析解决.
I've ever been to曾经去过,后面跟地点.