Of all that have tried, few have been seen as anti-Amazon as Marc Lore, Jet.com’s founder, has. An entrepreneur who previously founded the parent company of Diapers.com and later sold it to Amazon for $550 million, Mr. Lore and Jet.com were featured on the cover of Bloomberg Businessweek in January 2015 — before Jet.com had made a single sale — with the headline “Amazon Bought Marc Lore’s Company. Now He’s Coming for Them.”

From offices in Hoboken, N.J., Jet.com tried to chart a different course in the e-commerce market. It attacked Amazon directly, seeking to build a national network of warehouses while offering a similarly broad selection of goods. But it also sought to undercut Amazon on price, using complex formulas that adjust the cost of items based on factors like the quantity of products bought at once. For an annual membership fee of $50, Jet.com consumers could get access to goods priced 10 to 15 percent less than anywhere else on the web.

Mr. Lore also tried to make Jet.com different from other start-ups at the workplace. Most start-ups try to bend a reluctant universe to their will, which means employees sweat 12-hour days and seven-day weeks. Private lives go by the wayside. But Jet promoted itself as a start-up with a difference: one focused on employee well-being.

“I’m constantly asking people at Jet if they’re happy,” Mr. Lore said in an interview last fall. “It’s really important for me to know that they love working here and think this is the best place they’ve ever worked.”

His approach in e-commerce and the workplace may have seemed quixotic, but Mr. Lore succeeded in raising more than $500 million from many investors, including venture capital firms like New Enterprise Associates and the mutual fund company Fidelity. Jet.com quickly gained a valuation of roughly $1 billion.