I can help, I know a deal about Russia's personality
He can be cruel sometimes, but is much like a child and doesnt know he is being cruel. He is quite childish and one of his favorite flowers is a sunflower, he dreams of living in a place full of them. He is scared of his little sister Belarus and hides from her when she goes in 'Marry me' Phase, but they are shown they CAN get along at times. He is really kind and sweet but because of his scary demeanor (Much like Sweden except not intimidating, just plain scary) he doesnt have many friends, but wishes he did. He hopes everyone can 'become one' one day so he wont have to be lonely.