How to deal with colleague's complaint and to other colleague's criticism?

Just tell him in a polite way that you don't agree with him. Don't become confrontational. Try shaking your head while you're listening and when he asks why, just say that you don't agree.

Hi there jueyyan! I have several colleagues that keep complaining. Some of them, real chronic complainers. There are times when I really need to work and so I stay in my work station. I would hear them talk all day and it can really get irritating. When one comes to me and tells me how bad this and that is, I would listen and smile from time to time and nod from time to time. After a while, I would tell that person to go to the proper authorities to share his sentiments as telling it to me will never change a thing. Besides, he/she is barking up the wrong tree.

Agree with him to disagree

Just be yourself, just dont argue with him or her. Mind your own. Just think that you have lots of things to do and you must have a focus on your work. You must keep going and dont be affected on their criticism cause you know yourself better that they know you.=)