I’d go with “event source”, “event destination” / “event target”, or “event cause”, or “event effect”. If we’re talking about a database, it may even literally be a data trigger.

Was a matter of personal taste?

I think your confusion here arises from your assumption that there is one greatest thing. When do you think I have to consider it the greatest thing? In other words, you assume a strong order.

If there are two people in the world who are equally fast, who? Will I have to do it in one hour to run a mile? What are the ways to beat another miler by running in three minutes?

In this case there are two greatest runners, because they both have the best time, and neither is better than the other. Of course they go along side each other, and this is why they won the race. What are different examples of high-profile historical tragedies?

You will find that this is a very logical question. Not a grammar question. How does weak ordering work?