Merck KGaA CEO Karl-Ludwig Kley introduces his company's new branding. Merck KGaA When changing an established corporate logo, there's a fine line between success and disaster.

This year, several major companies changed their logos, and some simply fell flat.

To identify the worst revamps, Business Insider looked through graphic-design publisher UnderConsideration's Brand New blog archives and picked out our least favorites. We only considered large, non-athletic-team or university brands that rolled out the changes in 2015.

Take a look below to see some of the worst redesigns of the year: