In the organization of a company, it is inevitable that an employee always keep company with co-workers. Where I live, in Japan, success of work is accompanied by not only the skill of work, but also a good way of companionship of it. Personally, I believe that the important characteristics of co-worker are cooperation, positivity and perspective on work.
My primary reason is that cooperation and positivity are advantageous characteristics to proceed any work. One example of this is that a company is one organization which consists of plural employees, and aimes same one purpose. To attain it, cooperation with responsibility should be vital in senses of each employees. Also, work should be done in limitted time; the more amount of work remains, the more overtime work increases. I think that a positive attitude on work decreases extra overtime work; ask someone about work or challenge unknown work. However, if co-worker is not helpful and positive, he or she causes bad influences such as unbalanced amount of work or late pace of it. Overtime work might be forced to increase.
Another reason is that I prefer to work with co-workers capable of considering in coherent way. For example, as I have already mentioned above, a company is one organization that consists of plural employees. Each of them is allocated to specific positions by consideration; relatively more numbers of employees are allocated to place of more amount of work, but only one supervisor for it. Thus, even if certain number of employees are allocated to workplace with a simple or tough works, they are appointted to important part of a company; actually if one of them are absent from a company, amount of work per a person increases, and there might appear a possibility of overtime work. On the contrary, unless a co-worker have perspective on work, they tend to make themselves of nothing. They do not know the importance of their work, so that they scarcely have a responsibility of their work; they might mistake their work for sloppy acts.
My primary consideration with respect to which characteristic is the important as a co-worker's are whether how he or she can be helpful and positive, and whether to understand importance of his or her positions in company. Therefore, I think that co-worker should be helpful and positive, and have perspective on work.