Gor'ko!

Gor'ko! is an achievement in Metro Exodus that can be obtained in the level Summer.

Overview
This achievement is obtained simply by completing the level Summer on any difficulty. This is one of the intermission levels set aboard the Aurora, which doesn't involve any combat and rather allows the player to learn more about various characters and the story by listening to the dialogue between members of the Aurora's crew. This is a story-related achievement that cannot be missed.

Trivia

 * "Gor'ko" (Russian: Горько) literally means "bitter", but in the context of the Summer level a better translation would be "Cheers!" - the characters say this expression when making a toast as Stepan and Katya get married.
 * It's customary in both Poland and Russia to shout this phrase at weddings (in Polish it's written "gorzko" and pronounced "gozhko"), to encourage the bride and groom to kiss. Family and friends attending the wedding as guests, having drank plenty of vodka (as is customary at many Slavic wedding celebrations), will shout this phrase in unison until the newly wedded couple kiss to "sweeten" the taste of the bitter alcohol.
 * There's also a Russian movie with the same name which is essentially a wedding comedy - the use of this expression, same as the name of the achievement, might also be a reference to said movie.