I'm sorry you had all of this difficulty. Honestly... I wouldn't know what to suggest in the way of how to apologize. But I noticed no one had replied to your post. So I thought I would with the hope that other PC members may yet read it & have some suggestions to offer. On the other hand, it's been several days now since you posted this. Perhaps the situation has changed since then... or even resolved itself?

Toward the end of your post you wrote you are now neutral on this person & would prefer to go to a "never speak again" situation in group calls & such. So perhaps the best thing here may simply be to let bygones be bygones, as the saying goes, & forget about the need to apologize? Although you may feel apologizing is the right thing to do, it may just end up rekindling the whole dispute. Many years ago, my father used to say: discretion is the better part of valor. It may be best to simply let it all go & move on. At least that is my thinking with regard to your post. Best wishes...