Russia has sent its army to a few nations, such as Afghanistan and North Korea. But it has never tried to invade another nation using its army. Also, it has never tried to topple democratically elected governments.
What will you call Crimea War and annexation of Crimea then?
It was a direct attack and violation of sovereignty of Ukraine. Do you remember what Russia promised in Budapest Memorandum on Security Assurances?
Once Ukraine had the world's third largest nuclear weapons stockpile, they give up this arsenal for the promise of territorial integrity and assurances against threats or use of force against them by Russia.
Crimea was a part of the Russian Federation until 1954, and the population is overwhelmingly ethnic Russian. In 1954, the region was forcibly merged with Ukraine. So there is nothing wrong in Crimea returning to Russia.
And regarding nuclear weapons, Russia is regarded as the successor nation to the USSR. Only they were allowed to keep the nukes, and the other nations such as Belarus, Ukraine, Kazakhstan.etc gave up their weapons.
You Imperial psychology. The Russians somehow think themselves privileged nation. This is your problem. Except you no one else thinks so and it will contribute to constant conflicts. In the end, Russia will disintegrate into many small countries. So it was with the Soviet Union and Russia. As for Crimea then it is recognized as territory of Ukraine at the international level. Sooner or later the Crimea will return to Ukraine.