I would say Donetsk and Lugansk - way to nowhere 
The whole situation is very unclear in those 2 regions. Some minority desires to join Russia there (not more than 30% according to different polls), another part of people is against Russia and against Kyiv (against everything I guess)
Those who want to join Russia are backed by russian soldiers, who've actually invaded into neighbour state.
Those 2 regions are heavily subsidized, depressed regions, with out-of-date industry and terrible social sphere (crime level, fertility, life expectancy...). Ukraine spends on average ~ 5 billions USD per year to subsidize those 2 regions.
Taking all facts into account there are very big chances that Putin will not join those regions and has no real intentions to do this.
Speaking about the rest of Ukraine (including Kharkov), people are pretty united there and don't want to live in Russia. Just an example Kharkov football fans, yelling: "Putin XXXX"
https://www.youtube.com/watch?v=4G6oezjfSsU
The whole situation is very unclear in those 2 regions. Some minority desires to join Russia there (not more than 30% according to different polls), another part of people is against Russia and against Kyiv (against everything I guess)
Those who want to join Russia are backed by russian soldiers, who've actually invaded into neighbour state.Those 2 regions are heavily subsidized, depressed regions, with out-of-date industry and terrible social sphere (crime level, fertility, life expectancy...). Ukraine spends on average ~ 5 billions USD per year to subsidize those 2 regions.
Taking all facts into account there are very big chances that Putin will not join those regions and has no real intentions to do this.
Speaking about the rest of Ukraine (including Kharkov), people are pretty united there and don't want to live in Russia. Just an example Kharkov football fans, yelling: "Putin XXXX"
https://www.youtube.com/watch?v=4G6oezjfSsU
Normally I don't reply to 100% BS posts, but I will do it since this is your first post here.
1. It is not a minority. According to neutral polls, 60% to 80% want to join Russia.
2. No. There is no presence of any Russian soldiers there.
3. Subsidized? Can't stop laughing. Actually these two provinces produce the much needed coal and industrial output, which helps Kiev to subsidize the remaining provinces.