Question

What is the most major incident that you think transpired in 2015?

Answer 1

The terror attacks in Paris and the Russian aircraft...

Comments

Those two sure stand out.
I was going to put - don't include Sodahead quitting on us, where still here so that's the most important thing.

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I nearly put the flooding in Northern England and Scotland...it's been raining for weeks and the water is around four feet high into homes and businesses...

Answer 2

The Erosion of the U.S. Constitution

Answer 3

Russia's entry into the Syrian conflict.

Ostensibly they claim to be attacking ISIS but in fact they're supporting Assad by also attacking Syrian rebels. Add this to the hostilities in the Caucasus -- including the deliberate shooting down of MH17 --  and they look very threatening indeed.

Answer 4

The attacks in Paris will probably go down as this year's "9/11" even though it happened in France. Terrorist attacks of that size don't happen very often and the world's going to remember that one for a long time.

Comments

Islamic terrorist attacks on that scale in fact happen about once a month, only not in Europe or the Americas, so that's why we hear very little about them. Our PC MSM would not want to appear Islamophobic.

https://en.wikipedia.org/wiki/List_of_terrorist_incidents,_July%E2%80%93December_2015

Answer 5

That may not be apparent for some time.  Things that transpire later because an incident that happened this year may make that incident what 2015 is remembered for, even if the full import of it is not so obvious today.

Answer 6

The U.S. Supreme Court decision that legalized Same-Sex Marriage.