Who does win? Implies that winning doesn't happen often. Fx. if you're talking about different sports-teams and people are saying that most of the teams are losing all their matches, you could ask "who does actually win?" to inquire which teams are actually winning anything. Who wins? Is a question you could ask if you are faced with a no-win situation. Fx. you and your wife want to eat out, you love mexican food and she loves chinese food. You argue often and neither of you want to do what the other person wants, so instead of going to either restaurant you like, you decide to eat hamburgers instead. Who wins in this situation? If you are watching a game and you want to know who is winning the game, you can ask "Who is winning?"

Sofia has given you some very accurate examples of possible contexts when you might use simply the words "who wins" or "who does win". Thumbs up. My guess is that your question is about the need for the auxiliary verb "do" with "who" questions in the present simple and past simple tenses. If your "who" question has no subject because you want to know the subject (person), then you do not use "do/does/did". e.g. Who killed Roger Rabbit? Who needs help? Who is afraid of the big bad wolf? If your "who/whom" question has a subject and you want to know the identity of the object person(s), then you need "do/does/did". The exception to this rule is with the verb to be, which never takes the auxiliary verb "to do" anyway. e.g. Who did Roger Rabbit kill? Who do you need help from? Who is the big bad wolf afraid of?

Who wins? or Who does win >>> " Who won ?" or "Who will win?"

It depends on the other sentences. For example if you are using with a relative clause you can use as the first one like " I dont know who wins". Second one is a valid sentence and means something like "who does generally win?". Not for asking the result of a compatition. But I am not sure if you want to mean that. I think the correct answer is "who is the winner?"

It would be a lot of help to us if you provide a context or the full sentence. Thank you!