To my great disappointment, the project that I devoted so much time to  failed finally

参考译文：令我非常失望的是，我花了这么多时间的这个项目最后还是失败了 。

解答：以上填：“failed”  failed为动词过去式，不是过去分词。

备注(1): failed为动词过去式，不是过去分词。

备注(2):to my great disappointment为句子状语

备注(3):the project that I devoted so much time to为句子主语，关系代词that引导限制性定语从句，that代替先行词“the project”， 并在定语从句作介词to的宾语。

备注(4): that I devoted so much time to为定语从句修饰先行词“the project”

备注(5):failed为句子谓语动词

以上句子语法结构分析如下

To my great disappointment(状语),// the project (主语)//that I devoted so much time to (修饰主语后置定语) //failed(谓语动词)// finally(状语)

备注(6):finally为句子状语