russia sent its military across an international border and tried to decapitate ukraine's government. period.
also, unlike, say, syria, this is not a situation like venezuela where, whatever you think of ukraine's government, a huge majority of the people want something else. they voted for the people in charge. they are not begging for russia to come in and fix it.
this was, basically, when the USSR/CIS split up, russia let ukraine have the warm water port they had lusted for centuries for (crimea) and a useful mining area (the east). they thought, here, have the title, you're a friendly government. the ukrainians got sick of puppet governments and elected someone who represented them. russia then wanted take-backs. the lame excuse a la the nazis with france and poland was that USSR had colonized ethnic russians across the border who were no longer going to be allowed to pretend they were still in russia. if you think about this 5 seconds, this is like hispanic migrants here wanting to be taught only in spanish. and let's be real, this wasn't about the people, it was about the naval port and the coal and other mining stuff.
and that was before they hit the highway with tanks trying to topple the government in kiev.
last, anything you think ukraine does, russia does 10x worse. putin and orban are basically dictators who kill or jail political opponents, silence speech, close opposition media, etc. at which point the anti-minority and anti-gay stuff they do should take on a more baby nazi vibe. you think ukrainians are corrupt? have you read anything about eastern europe? you familiar with the panama papers and putin? like he may have billions sitting abroad.