Could Greenland defeat Russia in a war?

No. The Russians have more bears.

The whole population is a fraction of the size of the Russian army, so on that basis no. However, greenland is huge with hardly any people, so the Russians might have a hard time finding them.

No. Greenland could not defeat the security guards at Walmart.

They don't have an Army.

Greenland is a territory of Denmark. Also, Greenland population is less than 50,000 due to the extreme cold climate there, and has no any kind of military whatsoever, not even any type of a National Guard.

Denmark is part of NATO .........................

Greenland isn't even a country. It's a territory of Denmark. It has no army. Hell, it barely has any people. More people live in Kalamazoo, Michigan than live in Greenland. Russia, on the other hand, is in the top-10 most populous countries in the world and has the second-most-powerful military in the world.

. . . I just wonder where the hell that question is coming from . . . .

Russia would lose because the US and the Commonwealth would beat the crap out of Russia. Oh yeah, NATO might get involved.

why not?

No. It has a population of about 55,000. Greenland has no regular military.

Greenland has never lost a war.