This question had me wondering what we do with answers that only partially answer the question. I can't flag it for anything, but at the same time, I can't really edit it without making it like the other answer. So what exactly would be the right thing to do?
There is no requirement to completely answer a question. Partial answers are expected. Stack Exchange actually expects to average at least 2.5 answers per question. If every answer were complete, the average should be closer to 1.
If the answer is correct and doesn't duplicate another answer (as in the case that you linked), then you should upvote it. If it is incorrect, downvote it. If you think that there should be additional information in the answer, comment or post your own answer.
The other answer is more complete but if the newer answer is correct, it is not fully complete.