Let me separate two things:
1. argues about everything
2. is always negative
For the first point I would (and did) always take the road of: what are we here for? Its a job and everyone has to put an effort into to get the job done, that in the end pays all our bills. You and I need colleagues aiming to deliver, because no one expects the employer to go bancrupt in a sec, but competition is hard today. So while on the job, lets focus on deliver the best you can and I will do the same. If there happens to be a real problem, don't blaim or argue, be clever and show up with a solution.
For the second point, this is mostly not work related. These people carry something aroiund with them, that doesn't belong to the working environment (couple issues, troube somewhere, lack of satisfaction, no one to talk to, etc.). I like to give a hand and listen, but after work. Tell them to go for a walk or a beer, what ever suits, ask honestly and lend an ear. However there are people wallowing in self pity. Give them one chance to talk to you, if it works fine, otherwiese get rid of them!!! Theydon't want to change and will make your life miserable! You don't need this. There is a lot worth living for, but get rid of people tearing you down!
Once someone told me, that there are three ways to handle situations and circumstances, take one road, don't look back:
1. change it or
2. swallow it or
3. leave it