The strike causing so much violence and trouble finally ende

这个是非谓语
在你的句子中：
The strike causing so much violence and trouble finally 【ended谓语动词已经有了】 after both sides reached an agreement
那么另外一个动词cause 只能用非谓语形式 causing 现在分词,表示主动
你想用had caused 那么就要加料
如：
The strike【which had】caused so much violence and trouble finally ended after both sides reached an agreement