Discuss weaknesses in positive light always discuss how you plan to overcome it, some of the answers could be:

I am always willing to take up additional responsibilities, but I end up being over worked so now I am realistic about what I can do, so that I do work to the required standards

If you lack certain technical skill, which is not crucial for the job you can state that and say you are planning to take up a training course/certification to get over it

If you do not wish to discuss your weakness, you can say, I cannot compete with ABC