The clarity of your original question was not known and you have now received 2 totally different types of response. Now that you have made yourself a little more clear, I still don't fully understand what you are asking. What are you trying to consider? What are you looking to do? Combat negative review websites about your company? Make sure your website doesn't show up for search queries that deal with negative reviews? Onlyhimanshu, you need to better explain your question if you would like a better response. The reason people are not understanding you is because you are not very clear. You have received a number of good responses already based on the other posters trying to figure out exactly what you are asking.
Targeting "negative keywords" as explained above by sophie and karina is an entirely different question/approach and most used in Google AdWords campaigns. The problem with using catch terms such as cheap, low cost, free, etc. when your product or service is not cheap, low cost, free, etc. is you risk your bounce rate flying through the roof and dissatisfying your visitors. Trying to lure visitors and not delivering what they are looking for only hurts your site in the long run. This is not what the original question is about though, just thought I'd add a little more.
"Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime." Chinese Proverb