Software that solves a generic problem (chat, CRM, file storage) sold to every industry at once, where the market is huge but the competition is brutal.
Zoom did one thing (video meetings that just worked) and sold it to every industry on earth: schools, law firms, hospitals, startups, governments. When the pandemic hit in 2020 the user count went from 10 million daily meeting participants to 300 million in four months. The horizontal positioning was the entire reason that scale was even reachable, because the product didn't need vertical-specific work to onboard a school district versus a hedge fund.