Light spoiler
You are both right and wrong at the same time.
Zhenya doesn't give a fuck about his family. The only one, he has somewhat of a connection with, is his sister, and that is more HER doing that his. He'd probably let her die without much thought or remorse if it came down to it.
He definitely couldn't care less about the rest of his family. But that also extends to the whole of Russia, so, no, he does not give two fucks about 'promotions'.
His own government would LOVE (and will try) to eliminate him, because he is such a pain in the ass and only does, what he wants.
It is never explicitly stated but very VERVY heavy implied that he has ASPD and has been a little sociopath since his early childhood, if his brother is to be believed.
He actually isn't that much of a sadist lol. There is worse ML's out there in that regard. He is just following, what catches his interest (and right now, that Taekjoo) and as an unintended side effect, is catching feelings along the way. Feelings, he most definitely does not know, how to express in an even remotely healthy way.
first of all i love how he's questioning if he's gay or not like brother... you should of looked up a “Am I Gay” test
also WTF DOES ZHENYA WANT WITH HIM? HE LOOKS LIKE THE TYPE OF GUY TO TRADE HIM IN TO GET A PROMOTION OR JUST TO SEE HIM SUFFER.... and I'm also surprised he has a family... he looks like he would kill his whole family at a young age