Recent history makes it quite clear that western powers are the greatest imperialist threat to Ukraine

In 2013, the west offered Ukraine a loan with horrible terms, to effectively enslave the country to western banks/corporations (standard imperialist practice!). 

Russia offered a similar loan, but with hardly any terms attached. 

The Ukrainian government went with Russia’s offer, unsurprisingly. 

This ignited protests from some of the more pro-west section of Ukrainian society. They overthrew the government, with help from neo-Nazi groups, and with direct involvement from the US government. (To what extent I guess we’ll find out in 100 years time or so when CIA documents are released).

The new government accepted the west’s IMF loan, with its horrible terms allowing western powers to restructure the country in such a way that exploits its people and land for the benefit of western capital. 

For example, the EU is now able to push "modern agricultural production, including the use of biotechnologies,” - aka GMOs - onto the country; An unnecessary, and extremely harmful, form of agriculture, that exists to enrich corporations like Monsanto.