Most, practically all, translations translate the pronoun as "whom", with its apparent antecedent being "sons of disobedience" in verse 2. However, when I look at the sentence analysis resources, it seems that its antecedent is "trespasses" in verse 1, making the proper translation to be "which". The resource "Kairos: a begging Greek Grammar" agrees that it should be "which". This is on page 90, point 9.
Anyway, if there are any Greek scholars here that has the time to comment, I would really appreciate it! I know that this is off topic, but I have few that I trust so much in these matters for direct correspondence. And with so many translations and commentaries not considering that it might be "which", I just wanted to be sure before I develop the study lesson for our church's men's group.
Thanks.