Is the search result I found a knockout? Does it prevent registration of my trademark? How similar does it have to be, for my chances of registration to be nil?
It depends on a number of factors. The easy answer is to get a trademark attorney and provide the “knockout” along with your proposed mark. However, attorney judgments differ, and it’s all in the application of the law, which is open to argument. Generally, the likelihood of confusion factors apply, of which the most important are:
Similarity of the marks in appearance, sound and meaning. How close are they?
Similarity of the goods and services covered by the marks? Are they identical? What are the differences?
Channels of Trade. Are they sold side by side, or would consumers never see the marks together?
Number of similar marks in the Register. If there are a lot, the bar to registration is lower.
Please see my extensive analysis, with arguments for likelihood of confusion.