Would link building to a different brand be considered as black hat by search engines?

Would link building to a different brand be considered as black hat by search engines?
As the title says. For example if Nike would link build to Adidas (ignore the reasons why for now), would it be frowned upon in the SEO realm?

Thanks.
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Black hat marketing involves SEO activities that are against the norms of search engines. Hence, black hat marketing is unethical. It is difficult for the search engine alone to distinguish when black hat SEO is applied. Competitors can play a role by reporting cases of black hat marketing to the search engines, who will in turn ban or penalise the website. Despite the risk of ban, marketers still can go for black hat marketing because it helps in boosting up the page location in search result.

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